PAR 243A FINAL REPORT BRIEFING PRINT ENLARGER (BPE), PROTOTYPE MODEL

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04770A000500010062-9
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 56
• Document Creation Date: December 28, 2016
• Document Release Date: October 8, 2004
• Sequence Number: 62
• Publication Date: August 18, 1967
• Content Type: REPORT

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This document contains
25X1
1
PV'3 19)
PAR 243A
FINAL REPORT
Briefing Print Enlarger (BPE),
Prototype Model
18 August 1967
Prepared by:
+4s-H
HKI
25X1
Date: 14 September 1967
25X1
Approved by:
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SUMMARY
SUBJECT
TASK/PROBLEM
1. (Statement of Problem)
INTRODUCTION
2. - 4.
DISCUSSION
Page
1
APPENDIX - BRIEFING PRINT ENLARGER (BPE) SPECIFICATION A-1
Enlarger/3X - 15X Fluid Gate Enlarger)
6. The Optical Design
7. The Enlarger Arrangement
8. The Breadboard Model (PAR 202/224)
9. Performance of the Breadboard Model (PAR 202/224)
10. Focus Calibration and Performance
11. The BPE Prototype Design (PAR 243A)
12. The Objective Lens Focus Assemblies
13. The Negative Gate and Lamphouse Assembly
14. The X- and Y-Coordinate Indicators
15. Print Exposure Prediction
16. Print Stock Easel
17. The Electrical System
18. The Magnification and Focus Table
CONCLUSIONS
19. - 23.
RECOMMENDATIONS
24.
5. The Design Study (PARs 202/224, Briefing Print 3
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Figure
Title
Page
1 Enlarger Arrangement Concept fro
m the Design Study
7
2 Vertical Fluid Gate
13
3 Breadboard Model of BPE (PAR 202
/224)
15
4 The Prototype Model BPE
21
5 Close-Up of One of the Interchan
Lens Focus Assemblies
geable Objective
22
6 One of the Objective Lens Focus
on the BPE
Assemblies Mounted
23
7 The Six Objective Lens Focus Ass
emblies
24
8 Lamphouse with and without Conde
nser Lens
28
9 Negative Gate
30
10 Six Condenser Lens Assemblies
32
11 Engagement of Condenser Lens Ass
Lamphouse
embly into the
33
12 The Negative Transport, Film Vie
Y-Coordinate Indicators
wer, and X-,
35
13 Macbeth Quantalog Easel Photomet
er, Model EP1000-B
37
14 Easel Photometer Assembly Mounte
d to Enlarger
38
15 Easel Exhauster
40
Table Title Page
1 BPE Lens Performance with Blue Filter (Wratten 98) 17
2 Objective Lens Focus Mechanism 27
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It was desirable to have an enlarger which would be relatively simple
to operate, provide a wide range of magnification adjustable in small
increments, handle negative film rolls rapidly, provide for handling large
sheets of print stock easily, produce large prints, and have color print-
ing capability.
The Briefing Print Enlarger (BPE) which was built on this project has
a horizontal optical axis and provides continuously variable magnification
from 3X to 60X through the use of a family of six quickly interchangeable
objective lens and condenser sets. Two additional lens and condenser sets
are being developed on a separate project (PAR 245, BPE High-Magnification
Lens Sets) to extend the magnification range to 150X.
Negative film in roll form can be handled rapidly in all widths from
70mm to 9.5 inches. The negative is supported in a wet, glass-sandwich
gate during printing. The print stock is supported by a 40-inch square
vacuum easel. Exposure is controlled by varying lamp intensity and exposure
duration. Printing capability is provided for both black-and-white and
color materials. Exposure prediction is simplified by the presence of an
easel spot-photometer. The entire optical'system is isolated from building
vibration. Precision focus calibration for every easel setting and corre-
sponding magnification is built into the BPE and presented to the operator
in easily readable digital form. A within-frame coordinate measuring system
is provided, calibrated in millimeters, and presented to the operator by
digital display. The only service requirement is electrical, plus an outside
vent for expelling used, negative-gate fluid vapors.
Exhaustive testing indicates that the design requirements for the BPE
prototype were met.
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SUBJECT: Briefing Print Enlarger (BPE), Prototype Model
TASK/PROBLEM
1. Design, fabricate, and test a prototype Briefing Print Enlarger
(BPE) based upon tests and observations of the breadboard equipment de-
veloped on the combined PARs 202/224.
INTRODUCTION
2. It was desirable to have a new enlarger which would permit the
rapid production of many additional types of prints now required in aerial
reconnaissance laboratories and which would have improved performance in:
a. Ability to expose larger prints
b. Wider magnification range with adjustment in 0.25 to 0.4 percent
c. Handling of negative film rolls
d. Print stock handling
e. Color printing capability.
The BPE produced on this project may be considered the third-generation design
following the 20X Precision Enlarger and the 10-20-40X Precision Enlarger.
3. This project, as described in the Task/Problem, was authorized
on 13 December 1965 and the completed prototype instrument was delivered
to the customer on 28 June 1967.
4. The studies in which the basic concepts for this project were
developed and proved were performed on two earlier projects on this contract
which were authorized in April 1964. PAR 202, Briefing Print Enlarger (lOX
to 60X Enlarger) was authorized to provide design studies and breadboard
hardware to aid in the design of an enlarger for exposing 20- by 24-inch
prints in the lOX to 60X range of magnification from roll form negatives.
PAR 224, 3X - 15X Fluid Gate Enlarger, was authorized for similar studies
and for breadboard hardware to aid in the design of an enlarger to provide
3X to 15X magnification from 70mm square portions of roll negatives and
prints up to 40 x 40 inches on cut-sheet stock. Both of the requirements
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applied to either black-and-white or color prints. As the work on the
two projects progressed, it became apparent that a single basic enlarger
frame with a series of interchangeable lens and condenser sets would meet
both requirements. The two projects were therefore combined, and a single
breadboard unit was built and tested. When that effort was completed, a
proposal for this project was submitted. Instead of a written final report
on the breadboard effort, a verbal report was made to three groups of
customer personnel concerned. Information on those projects is presented
below as background for better understanding of this project.
DISCUSSION
5. The Design Study (PARs 202/224, Briefing Print Enlarger/3X - 15X
Fluid Gate Enlarger). The purpose of these projects was to provide an
enlarger having a negative handling system, a high-performance specular
optical system, and a glass-sandwich fluid-wetting negative gate similar
to the ones on the 10-20-4OX Precision Enlarger but with the extended
capability of exposing larger prints over a continuously adjustable range
of magnification. Design concepts were developed to balance the performance
of the various parts of the system and to match the system performance to
the needs of the user. Fabrication and testing of the breadboard model
permitted practical evaluation of its performance. The experience gained
in operating the breadboard model was very useful in refining the prototype
design for this project (PAR 243A) for better dependability and operator
convenience.
6. The Optical Design. To obtain 20- x 24-inch prints with an
instrument of reasonable size, the field-angle coverage of the objective
lenses was increased over that in the 10-20-40X Precision Enlarger. For
a given focal length in a lens design, increased field-angle coverage is
normally obtained at the expense of decreased performance on the lens axis.
It appeared that lenses having an axial performance somewhat less than the
lenses in the 10-20-40X Enlarger would preserve the information present in
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the most sophisticated aerial photography currently available. It there-
fore appeared reasonable to attempt the design of lenses with wider
fields. In the design study, a semifield coverage of 180 to 200 was de-
cided upon for the lenses. With this angular coverage a 20- x 24-inch
image is provided with a negative-to-easel (OAC*) distance of 50 inches.
By providing 30 inches range of easel movement, to obtain OAC distances of
50 to 80 inches, the desired range of 3 to 60X magnification for the com-
bined PAR 202/224 requirement was available with a family of six objective
lenses.
a. The system was designed for a glass-sandwich-type negative
gate, with index-matching fluid wetting of negative-glass interfaces, and
specular illumination. A condenser lens system was designed for each of
the six objective lenses to slightly under-fill the objective apertures
with the image of the projection lamp filament.
b. Since prints made at any magnification will be viewed under
similar conditions, the family of objective lenses was designed to provide
approximately equal image sharpness at the print. The effective exit-
pupil diameter (and therefore the diffraction pattern size at the print)
was made about the same for each of the six lenses of the set.
c. In the optical design of the objective lenses, initial effort
was upon a family of lenses which would expose color-blind print stock
through a narrow-spectrum-band blue filter. For this family of lenses,
the exit pupil was 0.6-inch diameter in the four lenses for magnification
values up to 25X and the exit pupil diameter in the remaining two lenses
was 0.45 inch. The Rayleigh criterion predicted 13 to 20 cycles/mm limiting
resolution at the print (for diffraction-limited lenses) with 80 inches OAC.
In the statement of design goals to the lens designer, it was requested that
90 percent of the computed rays fall within:
* Over-All Conjugate
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(1) A circle equal to the diameter of the first minimum
of the diffraction pattern to 60 off axis,
(2) A circle twice that diameter to 12? off axis, and
(3) A circle four times that diameter to 18? off axis.
Lenses meeting these requirements could be expected to produce prints
from "perfect" negatives which appear excellent under unaided visual
observation or when considered as copy for photomechanical reproduction.
d. The second effort in designing objective lenses for the BPE
was on a family of lenses to expose color print materials with narrow-
band, tri-color printing filters. The exit-pupil diameters were speci-
fied as two-thirds of those for the color-blind print material, with
the same type of specification for concentration of the computed rays.
As this effort progressed it became evident that most of the color-
corrected family of lenses could, with minor changes, also meet the
goals stated for the narrow-band, blue-light lenses.
e. A third effort was initiated to design "combination" lenses
which could meet both sets of design goals. This was achieved for the
five lenses of the family providing magnification up to 40X. Two differ-
ent lens designs are required to meet the goals for the 40X to 60X magni-
fication range. Because of the image quality in current and expected
color original films, it did not appear likely that color enlargements
over 40X will be required from the BPE. The 40X to 60X lens corrected
for blue light only was established as the sixth member of the family of
lenses.
7. The Enlarger Arrangement:
a. Studies of the enlarger arrangement were made concurrently
with consideration of field angle coverage and film-to-print distance for
the optical design. The 50 to 80 inches optical length was too great for
a straight vertical axis design because of limitations in head-room and
the inconvenient means for operator access to the negative and print
stock ends of the system. Various folded-optical-path systems were
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considered but offered little reduction in size of equipment. The
straight-horizontal-axis arrangement was chosen since it appeared to
offer the most convenience to the operator and had the simplest
mechanical construction.
b. The major mechanical requirements to be considered in
designing the equipment were:
(1) Image quality in the prints must not be degraded
either by building vibration or by vibration generated in the instrument
itself.
(2) The following must be provided:
(a) A safe, rapid-handling system for finding a
given image area in a large negative roll on the basis of frame number
and image coordinate description, and placing it in the negative gate.
(b) A convenient means for print stock handling.
(c) A means of setting the lens focus accurately for
any chosen magnification in the available range.
(d) The capability for exposing both black-and-white
and color prints.
(3) The instrument must be convenient, dependable, and safe
for use in critical, high-production operations.
c. It was, of course, necessary to develop one design concept to
meet all of these requirements. This arrangement concept, as developed in
the study, is shown schematically in Figure 1. Important features of the
enlarger design concept are:
(1) Vibration Control. The print stock easel and its carriage,
the objective lens, and the negative gate are mounted on the optical frame
to form an assembly of high rigidity. To prevent image degradation that
results from vibration, there must be no relative motion between the image
projected from the negative gate and objective lens combination and the print
stock held on the easel face during exposure.
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(a) The effect of external vibration (or shock from
the building) was eliminated by supporting the optical frame on shock
mounts which are soft enough to filter out the high-frequency part of
the external vibration which might excite resonance in the assembly on
the optical frame. This assembly must be quite rigid to ensure that it
has no low resonant frequencies. In the BPE, the optical frame assembly
was designed to eliminate any resonant frequencies below about 70 Hz,
and it is supported on shock mounts that provide resonant frequency of
15 Hz or less.
(b) Vibration in the assembly on the optical frame
caused by sources within the enlarger must also be avoided. Precautions
taken in the design to prevent such vibration are:
1. No motor or solenoid on the optical frame
operates during the time of an exposure.
2. The exposure is started and ended by turning
the lamp on and off; there is no mechanical shutter.
(2) Negative Handling. A proposed requirement for the
BPE was the production of single prints from various image areas in roll
form negatives having no more than one or two of the image areas in a
given negative roll. In this kind of operation, handling of the negative
rolls takes a substantial part of the total time required to produce the
prints.
(a) The concept for the negative transport was based
on designs the contractor's organization had produced for motorized re-
spooling tables under other contracts. In these designs, the film-spool
drive spindles are powered by a-c torque motors to which variable voltages
are supplied from a gang of variable autotransformers. Manual rotation of
the autotransformer shaft will simultaneously reduce the voltage supplied
to one torque motor, thus reducing its torque output, and increase the
voltage supplied to and the torque produced by the other. Manipulation
of the autotransformer control will therefore cause the film to (1) wind
in either direction between the two spools at adjustable speed or (2)
remain stationary.
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(b) Considerable speed and operation convenience is
gained by providing spindle brakes to stop and hold the film at a chosen
place. The spindle braking must be done carefully to prevent cinching,
excess tension, or production of a slack loop in the film. In the re-
spooling-table designs, a prony brake arrangement was used to brake the
supply spool moderately and the take-up spool lightly for either direction
of winding. To reduce the size and weight in the BPE transport, it was
decided to substitute commercial electric brakes (magnetically applied
friction brakes) for the specially built prony brakes of the original
system. A system of varying the brake torques (by varying the brake
coil voltages) in relation to the voltage applied to the torque motors
was proposed.
(c) A film-driven, metering-roll mechanism to measure
the along-the-film coordinate (X coordinate) was proposed. This mechanism
concept featured the capability to survive high-speed slewing of the films
and low frictional drag.
(d) The film transport arrangement permits the film
web to be moved in the direction of its width over an incorporated viewer
for observation and to position any point on the film width at the objec-
tive lens axis. Each of the film spindles is carried on a separate slide
assembly. Each of the slide assemblies is driven by a lead screw coupled
by toothed belts to their common drive motor to preserve the alignment
between the spindles that is necessary for good film tracking.
(3) Print Stock Handling. In the first discussions on the
lOX to 60X enlarger project (PAR 202), use of a roll holder for the print
stock was considered. Studies which were made on problems of vibration
control with a roll-holder system for the 20- x 24-inch prints indicated
serious problems. Discussions of operational requirements revealed that
there is often an urgent need to have a single print from a specified
image as quickly as possible. Use of cut-sheet print stock along with
suitable print processors could provide the quick response capability
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conveniently. The 3X to 15X enlarger project (PAR 224) required a 40-
x 40-inch easel area for 15X enlargements from the 70mm square negative
area. With the proposed optical system, each of the four higher-magnifi-
cation lenses of the family of lenses could expose 30- x 40-inch prints
at the 80-inch OAC setting. This would make the large easel face required
for the 3X to 15X enlarger (PAR 224) valuable for the lOX to 60X enlarger
(PAR 202) also. It was therefore decided to develop a 40- x 40-inch
easel for cut-sheet print stock to satisfy the requirements of both en-
largers. This decision was the final step which permitted the two enlarger
development programs to be combined.
(a) The horizintal optical axis of the enlarger and
the corresponding vertical easel face made vacuum holding of print stock
sheets very desirable. A rough breadboard model had shown the feasibility
of using a turbine-type vacuum pump (or blower) to produce a pressure drop
of about 0.5 psig through an easel surface made up of a grid of 0.06-inch-
dia holes with one-inch spacing. A pressure drop that small is adequate
to hold sheets 4 x 5 inches and larger (which are not curled) and the
pressure/flow rate characteristics of available commercial blowers permits
the holding of any size sheet from the smallest to one covering about 80%
of the easel surface with nearly the same pressure drop at the easel
surface. A major advantage of the system is that any size sheet may be
placed at any position on the easel face without any need for adjusting
the manifold control valves. To provide this convenience,approximately
2.5 horsepower is required to run the blower and a low noise level is
present. Neither of these is believed to be unreasonable in this project.
(b) Curled print stock is a difficult problem for any
vacuum holding system unless the edges can be mechanically held in contact
with the easel surface. In this easel, a number of semi-rigid strips are
laid over the lifting edges of the print stock and are held against the
easel surface by the vacuum.
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(4) The Lens-Easel Focus System. A major problem in making
high-definition enlargements is to assure that the focus setting of the
objective lens is accurate. Because the adjustment of the focus to best
visual sharpness was much less precise than necessary, both mechanical
and electrical analog autofocus systems were considered but rejected for
lack of precision. The focus control system which was recommended after
study uses an independent manual setting of the easel position and of the
lens focus position using calibrated scales. The corresponding easel and
lens settings are read from a numeric table.
(a) The easel position is controlled and measured by a
ball-nut, lead-screw drive. By restricting the easel position to a
discrete number of points spaced 0.2-inch apart over the 50- to 80-inch
OAC range, the table provides a lens focus setting for each position.
The 0.25 to 0.4 percent steps of magnification change available with this
arrangement are small enough to be a practical equivalent of "continuously
variable magnification".
(b) Experience with the 20X Enlarger and the 10-20-40X
Precision Enlarger indicated that lens focus position should be controlled
to a precision of about 0.0002 inch for the higher magnification lenses of
the BPE lens family. The interchangeable lens assembly design from the
10-20-40X Precision Enlarger consisting of one negative gate glass objective
lens and focus mechanism was adopted for the BPE. The design was modified
to display the focus setting on a three-dial mechanical counter.
(c) As a further aid in setting lens focus, the table of
corresponding values is mounted in an assembly coupled to the easel carriage
drive to display only the lens focus setting which corresponds to the
existing easel position.
(5) The Fluid Gate:
(a) The fluid gate arrangement as used in the 10-20-40X
Precision Enlarger was thought desirable for the BPE. In this arrangement,
the negative is clamped (using spring pressure) between two glass plates to
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NEGATIVE TRANSPORT
(VERTICAL TRAVEL
ABOUT 14 INCHES)
OBJECTIVE LENS IN FOCUSING ASSEMBLY
(6 INTERCHANGEABLE UNITS)
-PRINT STOCK
EASEL
(MOVES TO ADJUST
MAGNIFICATION)
'-FOCUS AND MAGNIFICATION
INDICATOR
Figure 1. Enlarger Arrangement Concept from the Design Study
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maintain flatness and focus position. A small quantity of refractive-
index matching fluid (tetrachloroethylene) is injected between the film
and glass surfaces (on both sides of the film with the gate open to
provide a clearance of 0.03 to 0.06-inch) before closing the gate.
(b) The horizontal optical axis of the BPE and the
corresponding vertical gate plane created a problem in holding enough of
the injected fluid in the gate area to achieve full-area wetting as the
gate closed. The design that was proposed for the vertical fluid gate
is shown schematically in Figure 2. The important difference is the
open Vee condition with a line contact between the bottom edges of the
gate glasses and the film at the time of fluid injection. Surface tension
holds a quantity of fluid in the bottom of the gate which is spread up-
ward through the gate area upon closing.
(6) Black-and-White or Color Exposure Capability:
(a) The color exposure procedure chosen for the BPE
provides for making exposures through red, green, and blue filters in
sequence. An automatic operating sequence was proposed in which the
filters are positioned one after another into the optical path for a
timed exposure through each. Color balance control by operating the
printing lamp at a different voltage level with each filter was also
proposed. This would be achieved by providing three variable autotrans-
formers each one capable of being connected to power the printing lamp
with one of the three filters in the optical path. A single timer would
control the exposure through each of the filters. In addition to con-
trolling the color exposure sequence, the BPE controls would provide for
a single exposure through the blue filter to achieve the narrow-band,
blue-light exposure proposed for best image sharpness when the lenses
for black-and-white print exposure are used. Extended exposures with
switch control of the lamp's operation was proposed for use in set-up
operations.
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OPEN
INJECTION
OBJECTIVE LENS, GATE GLASS,
AND FOCUSING ASSEMBLY
READY
Figure 2. Vertical Fluid Gate
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(b) The color filters were placed in the optical path
between the lamp and the negative gate to prevent either (1) degradation
of the image-forming beam or (2) lateral shift in the tri-color exposure
from manufacturing imperfections in the filters.
8. The Breadboard Model (PAR 202/224):
a. In the course of the design study, certain parts of the pro-
posed design were designated for breadboard testing. Models of the negative
transport and of the vertical plane fluid gate were started early in the
design study program. The performance of the new lens designs could best
be evaluated by using them to make enlargements. To obtain meaningful
results from such lens tests, a test bed much like the optical frame of
the proposed enlarger was required. A breadboard model of the complete
enlarger would provide a test bed for the sample lenses. Such a model
would also permit evaluation of other features of the design proposal such
as the rigidity of the optical frame, suitability of the focus control
system, the performance of the print stock vacuum easel, and the convenience
of the enlarger arrangement.
b. Figure 3 is a photograph of the breadboard model of the enlarger
built under PAR 202/224 to test the new lens design samples and various
mechanical designs and arrangements. The design principles used in the
breadboard model were those described in the discussion of the design study
above. In the course of the design work, two desirable innovations were
conceived and incorporated in the model. The first innovation involved (1)
use of an automatic computer to prepare the Focus/Magnification Table, (2)
design of the table display unit (Figure 3, Item 9) and (3) use of the
computer-data-output scroll as the table display copy. The second innovation
was the incorporation of a commercial photoelectric photometer which permitted
printing lamp intensity and exposure time to be pre-set. In the breadboard
model, the photometer was arranged to measure irradiance in an 8-inch-diameter
section of the image projected upon the print stock easel. Classification
controls similar to those used in commercial color printers were incorporated
in the output circuit of the photometer (Figure 3, Item 12).
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1.
Vacuum print stock easel
2.
Negative transport
3.
Y-coordinate counter
4.
X-coordinate counter
5.
Negative
viewer
6.
Lamphouse
7.
Negative
transport controls
8.
Print exp
osure controls
9.
Focus and
magnification tabl
e display unit
10.
Interchan
geable objective le
ns assembly
11.
Optical f
rame shock mount (o
ne of four)
12.
Photoelec
controls
tric photometer cla
ssification
Figure 3. Breadboard Model of BPE (PAR 202/22+)
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9. Performance of the Breadboard Model (PAR 202/224). In October
and November 1965, focus calibration and performance tests were made on
the breadboard model enlarger. High-contrast resolution targets having
the USAF 1951 format with spatial frequencies in the 80 to 800 cycles/mm
range and having clear lines in a high-density background (more than 2.0)
were used in focus and quantitative performance tests. High-quality,
original-negative aerial photographs (made on Kodak High Definition Aerial
Film, Type 3404 and having an estimated resolution of 80 to 90 lines/mm on
the film) were also printed on Kodabromide paper to provide practical
samples of the enlarger's performance.
10. Focus Calibration and Performance:
a. Focus calibration was performed by measuring the best focus
setting at each of the three easel positions for each of the six objective
lenses. A photographic focus series was made at each position (Wratten
96 filter, blue, and Fine Grain Positive Film print stock), and the prints
were examined to find the focus setting in the series which produced the
best edge-sharpness in the image. This data, combined with other measure-
ments on each of the lenses made on a visual lens test bench, was used as
the input for a computer program to generate the focus/magnification table
for the enlarger.
'b. A series of test prints was made of the high-contrast resolu-
tion target for five easel positions for each lens, on axis, using the lens
focus settings predicted by the computer run. These prints showed resolving
power equal to that observed for the optimum focus position in the focus
calibration measurements. Table 1 shows the measured field coverage of the
six lenses and the observed axial resolving power (high contrast) for the
sample lenses compared to the diffraction limit of resolving power (Rayleigh
criterion) for the relative aperture of each lens and the wavelength of the
light used.
GROUP 1
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AND DECLASSIFICATION
 no Approved For Release 2004/11/30 : CIA-RDP78BO477OA000qW k= WN "M 1=1
500010062-9
BPE Lens Performance with Blue Filter (Wratten 98)
Magnification Field Diameter
Range of Negative
Lens Min Max (Inches)
Observed Axial Diffraction Limit of
Resolving-Power Resolving Power
High-Contrast Rayleigh Criterion
(Cycles/mm) (Cycles/mm)
A 2.95X 5.24x 3.9 89 98
B 4.75X 9.04x 3.8 127 160
c 8.46x 14.7x 3.8 226 260
D 14.5X 24.4X 2.15 360 422
E 24.lx 39.6x 1.29 452 510
F 37.7X 61.5x o.82 64o 782
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 Approved For Release 2004/11/30 : CIA-RDP78BO477OA000500010062-9
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18 Aug 67
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(1) Demonstration Prints. A set of 18 black-and-white
demonstration prints was made on Kodabromide paper from a high-quality
aerial negative. A print was exposed to show the full field coverage
of each of the lenses at each of three positions of the easel (minimum,
maximum, and mid-range magnification). Image quality appeared to be
excellent over the entire field of each lens. The grain structure of
the negative film (Kodak High Definition Aerial Film, Type 3404) pro-
vided the only edges sharp enough to indicate how well the higher magni-
fication lenses of the series performed. The images of the grain structure
were separated over the full field of the lenses with only a minor indi-
cation of astigmatism at the edge of the field with the E and F lenses.
This set of demonstration prints was delivered to the customer at the
time of presentation of the verbal reports on the PAR 202/224 project.
(2) Color Performance:
(a) High-contrast resolution-target images, (black-
and-white as used above) were exposed with the A, B, C, D, and E lenses
on high-definition panchromatic film (Type 3404) through the red, green,
and blue filters proposed for color printing. The resolving power ob-
served in the blue-filtered images was essentially equal to that observed
in the tests exposed on the color-blind Fine Grain Positive Film. The
resolving power in the green-filtered images was less than that in the
blue-filtered images, and that in the red-filtered images was still less
than that in the green-filtered images. The loss of resolving power
was closely proportional to the diffraction loss from the successively
longer wavelength of the light transmitted by the green and red filters.
The lens performance for color printing appeared to approach the diffraction
limit also.
(b) In practical performance tests of color printing
that were made about a year after the resolving power tests above, prints
were exposed on SO 271 Reversal Print Film from a classified color original
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(9.5 inches wide) on SO 121 Reversal Color Film. In test prints at 12X,
20X, and 40X, the color rendition appeared excellent, and the information
content and edge sharpness appeared to match the image in the original
film.
11. The BPE Prototype Design (PAR 243A):
a. The basic design which had been developed and the performance
which had been demonstrated in the combined project PAR 202/224 was con-
sidered satisfactory, and the purpose of this project (PAR 243A) was to
design, fabricate, and test a prototype enlarger based on that design.
b. In conferences between the contractor and customer personnel
following tests and demonstration of the breadboard model, a list of design
changes was agreed upon for incorporation, in the prototype model. Some of
the changes were to improve safety and convenience over the designs which
had been used in the breadboard model to reduce cost. Other changes
resulted from recognition of better arrangements after using the model.
The changes formally agreed upon are listed below:
(1)
Changes in the objective lens focus assemblies:
(a) To make the mounting and interchange mechanism quicker
and safer to operate.
(b) To make the lens focus indication easier to read.
(c) To provide means for producing the correct lens-
focus setting for projection through negative support material of various
support thicknesses in addition to the emulsion-toward-the-lens condition.
(2) Changes in the negative gate and lamphouse assembly:
(a) To improve the mechanism for closing the fluid gate
and to modify the fluid pump to deliver additional fluid needed to fill the
large gate area.
(b) To provide a gate ventilation system to remove
immersion fluid fumes efficiently, and provide for the collection of excess
immersion fluid and its fumes.
(c) To provide means for evaporation and/or removal of
the immersion fluid from the film after the negative gate is opened and
before that section of film can be wound onto the roll.
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18 Aug 67
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(d) To use filtered air for efficient forced-air
cooling of the lamp, condenser lenses, and color filters.
(3) Changes in the X- and Y-coordinate indicators to make
them easier to read.
(4) Substitution of an easel spot-photometer for print
exposure prediction instead of the broad area photometer system attempted
in the breadboard model.
(5) Changes in the print stock easel to provide an opaque
flat-white surface for use in making paper base prints and a black surface
to use in making prints on transparent-base print stock.
c. In addition to the above specific design changes from the
breadboard model, it was understood that the new design should (1) include
changes to reduce the cost of fabrication of enlargers built after the
first model, (2) present a finished appearance, (3) be easy to service,
(4) have conveniently located operating controls, and (5) provide inter-
locks to reduce the possibility of damage to negatives.
d. Figure 4 shows two views of the completed Prototype Model
BPE. By comparing them with Figure 3, Breadboard Model of the BPE, many
of the design changes can be seen, such as elimination of the separate
control console and improvement in the appearance of the unit over the
breadboard model.
12. The Objective Lens Focus Assemblies (see paragraph ll.b.(l) on
page 19):
a. The new design for the objective lens focus assembly and the
mechanism for interchange of the assemblies is illustrated in Figures 5,
6, and 7. A common carriage assembly design (Figure 5, Item 1) with two
full-hand-size handles (Figure 5, Item 2) is common to all of the assem-
blies. In each carriage assembly there are a set of rollers (Figure 5,
Item 7) and register pins (Figure 5, Item 8) used in loading or unloading
and in locating the lens focus assembly on the enlarger. To install the
lens focus assembly, it is placed on the loading ramp (Figure 6, Item 4)
GROUP 1
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 Approved For Release 2004/11/30 : CIA-RDP78B04770A00050001006' 2`?"=A_
18 Aug C7
8. Print exposure controls (sub-control panel)
9. Focus and magnification table display unit
10. Interchangeable objective lens assembly
11. Loading ramp for objective lens assembly
12. Main optical assembly frame (on shock mounts)
13. Easel exhauster enclosure
14. Easel photometer meter unit
15. Fluid injection pumps and reservoir jars
16. Main electrical equipment cabinet
rototype Model BPE
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AND DECLASSIFICATION
Approved For Release 2004/11/30 : CIA-RDP78BO477OA000500010062-9
 SECRET
Approved For Release 2004/11/30 : CIA-RDP78BO477OA000500010062-9
1. Vacuum print stock easel
2. Dark screen pull-down cover for white
easel face
3. Negative transport
Ii. Digital display for X- and Y-coordinate
readout
5. Negative viewer
6. Lamphouse
7. Negative transport controls
Figure 4+. 7
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1. Carriage assembly
2. Lifting handles
3. Focus indicator assembly (mechanical counter
within cover is readable from the front of
the assembly)
4. Focus shift control knob and locking collar
5. Focus shift scale
6.' Knurled ring handle for lens focus adjustment
7. Roller for loading lens focus assembly (one
of four)
8. Register pin for positioning assembly (one of six:
four on bottom of rails, two on vertical surface
below gate glass)
9. Gate glass assembly
10. Spacer sleeve
11. Focus thread assembly
12. Objective lens
Figure 5. Close-Up of One of the Interchangeable
Objective Lens Focus Assemblies
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1. Support pedestal for lens focus assemblies
2. Locking lever for lens focus assemblies
3. Lens focus assembly
4. Hinged loading ramp (Can be lowered to clear
beam projected from objective lens)
1
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Figure 6. One of the Objective Lens Focus Assemblies
Mounted on the BPE
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1. Objective
2. Objective
3. Objective
4. Objective
. Objective
Objective
Lens A - 3.0 to 5.3X magnification
Lens B - 4.8 to 9.OX magnification
Lens C - 8.5 to 15.OX magnification
Lens D - 11+.5 to 214.7X magnification
Lens E - 21.2 to 1+0.OX magnification
Lens F - 38.0 to 62.5X magnification
Figure 7. The Six Objective Lens Focus Assemblies
& proved SEC proved For Release 2004/11 /30 : CIA-RDP
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Q07i@A0Q0WWQV08 DING
AND DECLASSIFICATION
 Approved For Release 2004/11/30 : CIA-RDP78BO477OA000500010062-9
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PAR 243A
18 Aug 67
manually, rolled along the ramp into position on the support pedestal
(Figure 6, Item 1), and locked into position by moving the locking lever
(Figure 6, Item 2) about 1/2 turn to the position shown. To lock the
carriage into position, it is first lifted and four pins are pressed
against the bottom surface of the rails on the support pedestal; the
carriage is then moved along the track and two pins are pressed against
the vertical reference plate on the end of the pedestal. The locking
mechanism provides a spring-load of about 200 lb to hold the carriage
against the register surfaces. The loading ramp is lowered so that it
clears the beam of light projected by the objective lens. The lens
focus assembly can be removed by reversing the steps in the above pro-
cedure.
b. Each lens focus assembly includes a gate glass (Figure 5,
Item 2), the focus thread assembly, the mechanical counter focus indi-
cator, and the objective lens. Each assembly is tested and calibrated;
it is then used as a unit. This unit construction is the principal
reason that the BPE can provide the focus accuracy necessary for making
high-quality prints. The following two changes in the breadboard model
were made in the design of this assembly:
(1) The focus indicator assembly was modified to make it
readable from a position near the optical axis of the system, and
(2) An adjustable link was added in the coupling between
the focus thread and the focus indicator to offset the lens focal plane
to positions outside the surface of the gate glass.
c. In this design, the amount of focus shift is adjustable by
a knob with a locking collar on the face of the assembly (Figure 5,
Item 4), and its magnitude is indicated by an adjacent scale (Figure 5,
Item 5).
d. The six assemblies for the prototype BPE are shown in
Figure 7. The basic design and many of the individual parts of the six
lens focus assemblies are the same. The differences among them are
primarily in:
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18 Aug 67
(1) The length of the spacer sleeve (Figure 5, Item 10).
(2) The range of focus adjustment.
(3) The amount of lens focus movement represented by each
count of the focus indicator, and
(4) The absence of the focus shift adjustment in the "A"
assembly.
The length of the spacer sleeve is varied to position the focus thread
assembly to accommodate the various focal lengths of the lenses of the
family. For the higher magnification lenses of the family (D, E, and F),
the lens barrel design was made to permit positioning the optical elements
from a common-mount shoulder position in the focus assembly.
e. The range of focus motion and the accuracy of focus position
vary widely in the family of six lenses. To permit the focus for each
lens to be set as rapidly and conveniently as possible, the lead of the
focus thread and the coupling ratio between the focus barrel rotation and
the focus indicator counter were made different among the assemblies.
Table 2 shows the required range of focus adjustment, the focus movement
per count of the focus indicator, the lead of the focus thread, and the
amount of barrel rotation necessary to cover the range of focus adjustment
for the various assemblies. The focus motion per count was selected so as
to provide roughly three to six counts for the range of acceptable focus
setting of each of the lenses. The range of acceptable focus settings
for the lowest magnification lens assembly was found to be great enough
that it is not necessary to adjust the focus setting for negatives mounted
in the gate with the emulsion side away from the lens.
13. The Negative Gate and Lamphouse Assembly (see paragraph ll.b.(2)
on page 19):
a. The new lamphouse design can be seen in Figure 4, Item 6; it
is also shown in close-up views (both with and without the interchangeable
condenser assembly in place) in Figure 8. The lamphouse is designed to
move through a range of about two inches on a track roughly parallel to
GROUP 1
SECR roved For Release 2004/11/30: CIA-RDP 8$6 4 1 S I I A1pgN09ADING
 "0 "MOW"
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Objective Lens Focus Mechanism
Nominal Range of Focus
Lens Lens EF Adjustment
Assembly (Inches) (Inches)
A 10.66 2.252
B 7.17 0.713
C 4.8o 0.246
D 3.06 0.090
E 1.90 0.032
F 1.24 0.013
Range of
Focus Motion Lead of Focus Barrel
per Count Thread Rotation
(Inches) (Inches) (Turns)
0.002 0.200
0.001 0.200
0.000625 0.03125
0.0003125 0.03125
0.0003125 0.03125
0.00015625 0.03125
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 W" " " " " " "
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1. Condenser lens assembly
2. Air filter
3. Handcrank for moving lamphouse
4. Main control panel
5. Vapor shield
6. Nylon brushes for fluid removal
7. Heat lamp for fluid removal
Figure 8. Lamphouse with and without Condenser Lens
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PAR 243A
18 Aug 67
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the optical axis of the objective lenses. Its motion is controlled by
a crank arrangement through a gear reducer driven by the hand-crank
(see Figure 8, Item 3).
b. The lamphouse portion of the negative gate is spring-mounted
on the front of the lamphouse to provide the closing sequence illustrated
schematically in Figure 2. The corresponding sequence for the gate on
the prototype BPE is shown in Figure 9. In this design, the moving
assembly which makes contact with the negative is of relatively low mass,
thus reducing the possibility of impact damage to the film or to the gate
glasses and restricting the force upon the film to essentially that pro-
duced by the springs.
c. The visible part of the system for removal of immersion fluid
fumes and the collection of excess immersion fluid is the vapor shield
(see Figure 8, Item 5). The space around the negative gate is enclosed
by the shield except for the slot at the top and along the two sides for
admitting the film web as it is lowered into the gate by the negative trans-
port. Air is exhausted from the bottom of the shield enclosure by a blower
having about 200 cu ft/min capacity and delivered to the building exhaust
system to be carried outdoors. The continuous flow of air inward through
the film slot, which combines with the normal downward flow of tetra-
chloroethylene fumes (the fumes are two to three times heavier than air),
effectively prevents the fumes from escaping into the work area. Excess
fluid from the gate and film drips into the liquid-tight bottom of the
shield enclosure where it evaporates, its vapor being carried away by the
exhaust.
d. Fluid is removed from the film after the negative gate is
opened by evaporating it into the air flowing through the vapor shield.
The negative transport is driven upward slowly, giving 15 to 25 seconds
for the fluid to evaporate. A heat lamp with a 10-inch-long filament and
operating at about 300 watts is mounted on one side of the film at the
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Gate Ready for Fluid Injection
1.
Glass
plate
spring-mounted to the front
2.
Glass
plate
mounted to the
rear
of the
Figure
9.
Negative
Gate Fully Closed
of the lamphouse
objective lens focus assembly
Gate
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top of the vapor shield (see Figure 8, Item 7); its purpose is to raise
the film and fluid temperature slightly to accelerate the evaporation
rate. Some of the excess fluid from the negative gate forms a bead along
the bottom edge of the negative web. In a normal printing cycle, there
is sufficient time for that bead of fluid to evaporate before the negative
is removed from the gate, However, a means of removing the bead of fluid
was provided for the occasional unusual situation in which the negative
web is removed from the gate immediately after fluid injection. Two long,
nylon-bristle brushes (see Figure 8, Item 6) are provided, one on each
side of the film; they are moved to contact the bottom edge of the film
as the negative transport moves upward. The surplus fluid is removed
into the brushes by capillary action except for a thin surface layer which
evaporates in the normal manner. In some cases, complete removal of the
fluid bead is not accomplished because it spreads along the film web beyond
the ends of the brushes. It may therefore be necessary for the operator
to wipe the bottom edge of the film if the gate is opened sooner than
normal after the injection of immersion fluid.
e. A separate condenser lens and lamp assembly is provided for
each of the six objective lenses discussed in the section on the optical
system design study for the breadboard model. Each condenser and lamp
assembly is mounted on a plate which serves as the top cover for the
lamphouse. The six condenser lens assemblies for the BPE Prototype Model
are shown in Figure 10.
f. Cooling of the lamphouse, condenser elements, filters. and
lamps by forced air is accomplished using a flexible tube connected to
the vacuum easel exhaust system to exhaust air from the bottom of the
lamphouse. The air entering the lamphouse is passed through a filter
(Figure 8, Item 2) and then upward through two ducts (Figure 11, Item 7)
into the plastic cover of the condenser lens assembly (Figure 11, Item 3).
That cover acts as a manifold to distribute the flow of air into slots
in the mounting plate and downward over the condenser elements, filter
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Figure 10. Six Condenser Lens Assemblies
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1. Main body of lamphouse
2. Mounting plate for condenser assembly
(lamphouse cover plate)
3. Ventilation air manifold of condenser assembly
4. Filter wheel assembly
5. Positioning rods for filter wheel assembly
6. Positioning rods for lamphouse cover plate
7. Ventilation air ducts
8. Sockets for positioning condenser assembly
Figure 11. Engagement of Condenser Lens Assembly into the Lamphouse
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wheel and the lamp. Each mounting plate is cut out as required to guide
the flow of air to the proper area in its particular assembly.
g. The filter position for each of the condenser designs is
different with respect to the negative gate position. The filter wheel
assembly is mounted on a ball bushing slide mechanism which permits it to
be positioned to fit into the space provided in a given condenser assembly.
Each condenser assembly has two pairs of guide rods which provide semi-
automatic positioning of the filter wheel and the condenser assembly (see
Figure 11). To lower a condenser assembly into the lamphouse, the two
longer rods (Figure 11, Item 5) are inserted in the filter wheel assembly
to align the filter wheel with the condenser optics. By lowering the
condenser further, the two shorter rods (Figure 11, Item 6) can be inserted
in matching sockets (Figure 11, Item 8) in the main lamphouse body.
14. The X- and Y-Coordinate Indicators (see paragraph ll.b.(3) on
page 20):
a. For the new BPE design, the cylindrical-scale system for the
display of image-position coordinates in the negatives was replaced by
analog-to-digital converters with digital-display projectors. The arrange-
ment of the display units and the metering roller drive for the X-coordinate
system is shown in Figure 12.
b. It was possible to provide digital display of the image co-
ordinates in 3/4-inch-high numerals by minor adaptation of commercially
available equipment. The adjustment of scale readings to correspond with
fiducial mark locations on the film is accomplished by slip-clutches in
the coordinate system drives.
15. Print Exposure Prediction (see paragraph ll.b.(4) on page 20):
a. The technique of projection print exposure determination
(prediction) by photometry of a small spot in the image projected on the
print stock easel is widely used in commercial and aerial photo labs.
Since operators in the customer's laboratories were already skilled in this
technique, it was agreed that the BPE should be so equipped to eliminate the
need for training in another technique.
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1. Film spool drive
2. Outboard film spool support
3. Metering roll for X-coordinate (horizontal) measurement
4. Idle spool in film transport
5. Manual adjustment knob for horizontal positioning of film
6. Interchangeable condenser assembly
7. Lamphouse
8. Film viewer
9. Digital display of X-coordinate
10. Zero adjustment for X-coordinate
11. Digital display of Y-coordinate
12. Zero adjustment for Y-coordinate
Figure 12. The Negative Transport, Film Viewer, and
X-, Y-Coordinate Indicators
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18 Aug 67
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b. No easel photometer design was available which provided
sufficient response for making color prints on the BPE with a suitably
small aperture. Although the basic sensitivity of the Macbeth Color
Analyzer, Model EP-1000 was found to be adequate, the transfer of energy
from the probe aperture to the photomultiplier cathode was too inefficient.
A breadboard model of an optical system which would improve the efficiency
about 100 times was built and test results were satisfactory. The de-
velopment of a special model of the Macbeth Color Analyzer-the Model
1000B-was subccontracted and the prototype model installed on the proto-
type BPE.
c. The special easel photometer assembly is shown in Figure 13.
The probe assembly, Item 3, is placed in the projected image at the easel
surface. The light which enters the 3mm-diameter aperture in that assembly
is carried by the fiber optics bundle, Item 4, to the cathode of an end-on
photomultiplier tube in the photomultiplier type housing, Item 1. This
arrangement provides a low mass assembly for placement on the enlarger
easel and allows the photomultiplier tube and its enclosure to be firmly
mounted upon the enlarger. These benefits were of particular value for
the vertical easel surface arrangement of the BPE.
d. Figure 14 shows the installation of the EP 1000-B easel
photometer on the prototype BPE. The photometer meter box is positioned
to make its scale readable by an operator standing at the sub-control
panel (Figure 4, Item 8) where the exposure time and lamp intensity con-
trols are located. Item 3 in Figure 14 shows the probe assembly mounted
on a plastic adapter for holding it on the vacuum easel surface. The probe
assembly is surrounded by a foamed elastomer ring to provide protection
from accidental damage.
16. Print Stock Easel (see paragraph ll.b.(5) on page 20):
a. It is expected that the majority of the prints exposed on the
BPE will be on paper-base stock. Tests and experience have shown that no
serious flare effects arise in such prints from placing the print stock
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Approved For Release 2004/11/30 SE -RIF8B04770A000500010062-9PAR 243A
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1. Photomultiplier tube housing
2. Photometer meter box
3. Probe assembly
4. Fiber optics bundle
Figure 13. Macbeth Quantalog Easel Photometer,
Model EP1000-B
SEEPPfiled For Release 2004/11/30: CIA-RDP78BO
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 Approved For Release 2004111/.3Q:.GLA -RDP78B04770A000500010062-9
(, Kt I PAR 243A
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t
1. Photometer meter box
2. Photomultiplier tube housing
3. Probe assembly
4. Fiber-optics bundle
5. Filter selector knob
6. Cable connecting meter box to the photo-
multiplier tube housing
7. Blower which exhausts vapor fumes from
the negative gate
8. Receptacle for power cord of easel exhauster
9. Power cord for easel photometer assembly
Figure 14. Easel Photometer Assembly Mounted to Enlarger
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upon a white easel surface. Such a surface is convenient for observation
of the projected negative image in preparing to make a print. In the
breadboard BPE, the easel surface was of diffusing white acrylic plastic.
There is considerable lateral spread when an image is projected on this
material which destroys the apparent sharpness of the projected image.
It was necessary to provide an opaque white coating to obtain the desired
sharpness of the image when viewed on this easel surface. An acrylic
plastic sheet like that used in the breadboard BPE was coated with flat
white lacquer for the easel face of the prototype BPE.
b. When prints are exposed on transparent-base print stock, they
show flare effects if exposed over a white easel surface. To provide a
black backing when such prints are made, a porous black cloth can be laid
over the vacuum easel surface. The cloth will be held in place by the
vacuum; the cloth also allows air to flow through the easel face and to
hold a sheet of print stock in place. The black cloth is mounted in a
roller storage assembly across the top of the easel (Figure 4, Item 2).
From this position, it can be conveniently pulled down over the easel
surface when required.
c. The easel exhauster uses the same type commercial blower that
was used with the breadboard BPE. Because of its relatively high rate of
air flow (above 600 cu ft/min), it is desirable to locate the exhauster in
the room with the enlarger so as not to disturb the darkroom air-distri-
bution system. The blower was placed in an acoustic enclosure to eliminate
noise in its exhaust air stream. Two views of the easel exhauster are
shown in Figure 15: a front view of the assembly in operable condition,
and a top view with the cover removed to show the labryinthine path for
the exhaust air flow. The enclosure surfaces are covered with foamed
elastomer which absorbs acoustical energy.
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1. Safety cutoff switch
2. 7-inch I.D. flexible tube
connecting rear of easel
with the exhauster
3. Exhaust ports
4. Turbine blower
5. 3-hp induction motor
Figure 15. Easel Exhauster
Top View (cover removed)
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17. The Electrical System. In the new design of the BPE, consider-
able engineering effort was spent on the electrical system (a) to improve
the dependability of the equipment, (b) to physically integrate the
electrical components and controls into the BPE structure, (c) to provide
interlocks to protect the negative film, and (d) to provide indicators to
aid the operator in controlling the enlarger. The Operation and Maintenance
Manual has detailed descriptions of the electrical system and the enlarger
controls.
18. The Magnification and Focus Table:
a. In the discussion of the breadboard BPE project, the customer's
photo laboratory representatives expressed a desire for magnification up to
150 diameters. After preliminary consideration, it appeared that the upper
limit of the magnification range could be extended beyond 60X to about 150X
by providing two additional lens sets. On 9 June 1966, a project (PAR 245,
BPE High-Magnification Lens Sets) was authorized to develop those lenses.
The BPE design program had been modified earlier to provide the capability
for two additional lens sets, for a total of eight. The revised design
of the focus-and magnification table display unit (Figure 4, Item 9) pro-
vided for eight columns of data, and the computer program was modified to
calculate and print a table for up to eight lenses.
b. At the same time that these changes were made in the computer
program, it was rewritten into FORTRAN H language for use on the IBM 360
computer which then became available in the contractor's facility. The
program logic was also refined to make the magnification values which are
printed in the table more accurate. Even with these refinements, however,
the values shown for magnification may be in error by ? 1% because they
are dependent on focal length measurements and not on calibrated magnifi-
cation data.
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CONCLUSIONS
19. The prototype model BPE which was fabricated, tested and
delivered to the customer's facility, met design requirements.
20. This project provided a precision enlarger of new design for
the aerial photo reconnaissance laboratory. The new precision enlarger
provides improved performance in:
a. Ability to expose large prints,
b. The wide range of available magnification with effectively
continuous range of adjustment,
c. Handling of negative film rolls,
d. Print stock handling, and
e. Color printing capability.
21. A specification for the BPE was developed as part of the design
program and in conferences with customer's representatives (see Appendix A).
The performance of the prototype model was equal to or superior to these
specification requirements.
22. The set of manufacturing drawings which were prepared are suitable
for fabrication of additional instruments by a competent optical equipment
shop. These drawings depict the prototype instrument as delivered to the
customer and in that form are under document change control.
23. The operational manual which was prepared and delivered to the
customer with the prototype instrument was a preliminary edition which can
be revised and released in more permanent form under another contract after
more experience has been gained in production operation of the prototype BPE.
RECOMMENDATIONS
24. Make a description with price and delivery quotation for the BPE
available to other photo-reconnaissance laboratory groups.
GROUP I
/1aQQMgI WDING
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PAR 243A
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BRIEFING PRINT ENLARGER (BPE) SPECIFICATION
1
1. EQUIPMENT APPLICATION
The enlarger shall be designed for rapid, convenient production of
large photographic prints for unaided visual observation, as in group
briefing or for report illustrations, from high-quality aerial photo-
graphic negatives in roll form.
2. DESCRIPTION
2.1 The enlarger shall have a horizontal optical axis with a movable
print-stock easel to provide a range of negative-to-print distance from
50 to 80 inches. The print-stock easel, lens, and negative gate are to
be rigidly coupled together by a massive steel structural member which is,
in turn, isolated from environmental vibration by rubber-in-shear mounts.
2.2 The easel surface is to be 41 inches square and provide vacuum
holding for cut-sheet print stock at any position on that surface.
2.3 A magnification range of 3X to 60X, with the range of negative-
to-print distance described above, is to be achieved for black-and-white
prints with a specially designed set of six lenses. The focal lengths of
these lenses were chosen to provide a continuous range of available magni-
fication, as shown in Table A-l, page A-2. Five of the six lenses are
also suitable for color printing, providing magnification from 3X to 39X
for color prints. To provide the necessary focus accuracy, each lens is
to be mounted in its own focusing assembly, including a negative gate
glass.
2.4 The required focus setting for each of the six lenses for various
negative-to-easel distances (steps of 0.2 inch through the 50- to 80-inch
range) will be displayed in a mechanism coupled to the easel drive to show
only the focus setting and magnification for the particular lens and nega-
tive-to-print distance which exists. The lens focus will be set manually
to make the focus indication counter on the focusing assembly agree with
the displayed value from the tabulation.
GROUP 1
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JC C S Ff A I
 MGM M M M M M M M I M - = - r - i - - "
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Nominal Magnification, EFL,* f-number, Minimum Axial Resolution,
and Field Diameter Requirements
Nominal Minimum Minimum
Magnification Lens Axial Resolution Field Diameter
M OAC EFL f- Negative Print Negative Print
(Diameter) (Inches) (Inches) Number (Cycles/mm) (Cycles/mm) (Inches) (Inches)
2.95 57
3.77 65 10.75 17.8 80
5.24 80
4.75 50
6.48 62 7.17 12 113
9.04 80
8.46 50
11.0 62 4.85 7.8 200
14.7 80
14.5 50
18.5 62 3.06 5 320
24.4 80
24.5 50
30.8 62 1.90 4.2 400
40.3 80
38.5 50
48.2 62 1.24 2.8
62.7 80
* Effective focal length
27 10.9
21 3.7 13.9
15 19.4
23 17.6
17 3.7 24.0
12 33.4
23 31.3
18 3.7 40.6
13 54.4
22 30.5
17 2.10 38.8
13 51.1
16 30.4
13 1.24 38.2
10 50.0
30.4
0.79 38.1
49.5
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2.5 The illumination is to be produced by 300-watt tungsten pro-
jection lamps with condenser lenses. A separate condenser and lamp
assembly is to be provided for each objective lens, and the assemblies
are designed for convenient interchange in the lamphouse.
2.6 A three-aperture filter wheel whose position is selected from
the control console shall be provided in the lamphouse. The filters
are to be readily interchangeable to provide optimum exposure conditions
for a variety of print materials.
2.7 Exposure control is to be accomplished from a control box on the
side of the main enlarger frame. Exposures are started and ended by turn-
ing the projection lamp ON and OFF. The exposure time is controlled by
a decade timer for times up to 111 seconds in 0.1-second steps. (Effect-
ive exposure is proportional to exposure time for exposure time greater
than two seconds.) Irradiance level in the projected image is controlled
by adjusting the voltage applied to the lamp. Three variable autotrans-
formers are connected in such a way that a particular transformer supplies
power to the lamp for each particular position of the filter wheel.
Provision shall be made for extended-time projection through any of the
filter positions for image observation or photometer measurement of the
projected image. Timed exposures must be possible through any of the
three filters as selected at the control box or through all three in
sequence with the same time of exposure for each.
2.8 The roll-negative transport system shall wind the web horizontally
between the two spindles mounted with their axes vertical. The transport
system is to be movable up and down by a motor drive to place the film in
front of a viewer or to lower it into the negative gate with the ability
to place any point on the width of the web at the optical axis. Negatives
70mm to 9.5 inches wide mounted in flanged film spools (MS 26565, 12 Sept
62) up to 7.6 inches in diameter must be capable of mounting on the
transport.
I
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 Approved For Release 2004/11~t /, ,QCC :B,DP78B04770A000500010062-9
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2.9 In the negative gate, the film is to be clamped between glass
plates under spring pressure to hold it in the correct focal plane.
When the gate is partially closed, it must be possible to inject a small
quantity of index matching fluid (tetrachloroethylene) on each side of
the film which sets the film and glass surfaces over the gate area upon
full closure of the gate.
2.10 Interlocks are to be provided to prevent moving the negative
while it is clamped in the gate. A ventilation system must be provided
to remove the fumes of the immersion fluid to an outdoor exhaust. After
the gate is opened, the transport system must be driven upward to move
the wet film area past a liquid removal unit before it is possible to
wind the film by motor drive into either spool.
2.11 An easel spot photometer is to be provided to aid in predicting
correct print exposures for black-and-white or color materials.
2.12 A coordinate measuring system is to be provided to aid in posi-
tioning in the printing gate images which are described to the operator
by coordinates of position within a given numbered frame of the roll of
negatives. The unit of coordinate measurement in the system will be one
millimeter.
3.1 The nominal values of magnification (M), effective focal length
(EFL), and relative aperture (f-number), are given in Table A-1 for the
six lenses. The magnification achieved for a given negative-to-print
distance (OAC) may vary ? 2 percent for various lenses of a production
lot. The magnification value shown in the focus table may be in error
by ? 1 percent from the true value.
3.2 The minimum axial resolution requirement of Table A-1 shall be
applied to tests made in the following manner.
SECR/ff roved For Release 2004/11/30: CIA-RDP7
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~#~J~[~fi~]'AkYk111g1Fy1~AD ING
 Approved For Release 2004/11/30 : CIA-RDP78BO477OA000500010062-9
SEC RET
PAR 243A
18 Aug 67
3.2.1 The test target material shall have at least 100:1 contrast,
be in the USAF 1951 format, and provide 40 to 800 cycles/mm. The
material shall have been exposed on Kodak Type 649GH film on the Microscope
Resolution Target Camera at the contractor's facility. The test target
polarity will be clear lines in a high density background.
3.2.2 Test prints on the BPE are to be exposed on Kodak Fine Grain
Positive Film (or on equal product) with a Wratten 98 (W98) blue filter
in the lamphouse filter position.
3.2.3 Resolution performance will be judged as the highest spatial
frequency in the test target whose image is visually resolved in the print.
The criteria for judgment of image resolution shall be those of Paragraph
3.6.2 of MIL-STD-150A.
3.2.4 An exposure series may be exposed to obtain the optimum resolving
power. The lens focus setting shall be that predicted by the focus table.
3.3 The off-axis resolving power shall be measured at the same focus
and exposure which provided the axial resolution data and to the same
criteria. The same type of test target material shall be used, preferably
on a common piece of film. The arithmetic average of radial and tangential
resolving power for four radii of the field of view, separated by 900, at a
radial distance of 70 percent of the full field radius, shall be no less
than 70 percent of the resolution measured on-axis.
3.4 The minimum field diameter at the negative, as specified in Table
A-1, is primarily controlled by the various aperture diameters in the con-
denser system. The field diameter at the print is determined by the field
diameter at the negative and the magnification. The specified field dia-
meter at the print shall be measured with the negative-to-print distance
adjusted to produce the corresponding magnification given in the first
column of Table A-1.
SECR CROUP 1
~4Tproved For Release 2004/11/30: CIA-RDP6
 Approved For Release 2004/11/30 : CIA-RDP78B04770A000500010062-9
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3.5 The temperature of a photographic density sample having a uniform
density of 1.0 shall not be high enough to damage the sample at the stable
temperature level. A sample of Type 3404 film shall be flashed and machine-
processed to produce the required density. The film sample is to be in-
serted in the gate with immersion fluid and the enlarger is to be operated
for twenty minutes continuously with the lamp at 115 volts and no filter in
the filter wheel. At the end of this test, the film sample must show no
evidence of heat damage.
3.6 The enlarger (4.80-inch lens, on-axis) shall provide exposure in
sixty seconds on Kodabromide F2 paper to produce 0.1 density above fog level
through a density of 2.0 (ASA diffuse density) in a Kodak Photographic Step
Tablet with the W98 filter and the lamp operating at its rated voltage for
25-hour life at 80 inches OAC.
3.7 The log illuminance in the projected image of an open gate shall
not decrease more than 0.30 below that on the axis at a point 0.8 of the
maximum field radius from the axis.
3.8 The digital output of the coordinate measuring system, in either
X- or Y-coordinate, shall be within 1 percent of the actual sample movement
in millimeters, or within one count, whichever is greater.
3.9 The time-of-exposure as produced by the Lektra Labs Model TM-8
timer shall be within ? 5 percent of the timer setting for settings between
3.0 and 110 seconds. The variation of time-of-exposure for a succession
of five exposures shall not exceed a range of 4 percent of the mean time-
of-exposure for the set.
3.10 It is of extreme importance that the negative transport assembly
or the negative gate and exhaust shroud not damage the valuable negatives
to be printed by the Enlarger. Those areas shall be free of sharp corners,
sharp edges, or burred surfaces which may scratch the film. A practical
test to detect such items should be made by installing a piece of fresh,
flashed, and processed film. The film should be run in both directions
across the viewer and through the gate area. The gate should be closed
SECR,proved For Release 2004/11/30: CIA-RD
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with fluid injection and opened with the drying cycle, with the same
film sample. The film should then be examined for possible damage in
those handling operations.
4. ENVIRONMENT, SPACE, AND SERVICE REQUIREMENTS
The requirements of the Enlarger in these respects are given in
the Installation Engineering Data, Drawing Number 1-023-B-513.
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AND DECLASSIFICATION
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