COMMENTARY ON EVALUATION OF POLARIZER FOR USE IN OBLIQUE AERIAL PHOTOGRAPHY

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04549A001100020048-2
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 1
• Document Creation Date: December 28, 2016
• Document Release Date: June 18, 2010
• Sequence Number: 48
• Publication Date: December 20, 1968
• Content Type: CABLE

Sanitized Copy Approved for Release 2010/06/18 :CIA-RDP78B04549A001100020048-2
G F r. R E T 2016122 DEC 68. CITE
SUBJECT : COMM YON EVALUATION OF POLARIZER FOR USE IN
BOTH REPORTS (PART I AND PART II) ARE TECHINCALLY
A
.
VALID. ON PART II, THE IMAGERY EXPOSED THROUGH THE W12/POLARIZ
FILTERS PROVIDED SIGNIFICANT IMAGE ENHANCEMENT AS COMPARED TO
THAT EXPOSED THROUGHOUT THE W 12 FILTER.
B. BOTH REPORTS NAVE VERY LITTLE IN COMMON WITH OPERATION
SYSTEMS DUE TO CURRENT ACQUISITION ALT ITUDE5, I.E., EFFECTS OF
POLARIZATION AT 70,000 FEET ARE PROBABLY DIFFERENT THAN AT
LOWER ALTITUDES. ALSO THE EST WAS FLOWN WIT
AN AIR SPEED OF 85 KNOTS, OPERATIONAL SPEEDS ARE MUCH FASTER
(HENCE IMAGE MOTION COMPENSATION CONSIDERATIONS VARY>.
2. IT SHOULD, HOWEVER, BE RECOGNIZED THAT A POLARIZER FILTE
PAGE 20 531? S E C R E T
REDUCES THE AMOUNT OF ENERGY (APPROXIMATELY 9J.9 LOG EXPOSURE;
3 F/STOPS) REACHING THE RECORDING MATERIAL. TO COMPENSATE FOR
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REDUCTION, A FILM WITH A FASTER EMULSION SPEED MUST BE USED OR T
EXPOSURE MUST BE INCREASED. EITHER OF THESE OPTIONS MAY RESULT
A LOSS OF GROUND RESOLUTION DUE TO TKE INCREASED GRANULARITY OF
A FASTER FILM OR IMAGE SMEAR INTRODUCED THROUGH LONGER EXPOSURE.
3. POLARIZATION IS EFFECTIVE IF RIGIDLY COORDINATED WITH FLI
AND EXPOSURE PARAMETERS, I.E., SOLAR ELEVATION AND AZIMUTH RELAT
TYPE OF RADIATION, SCATTERING INVOLVED, E
TO CAMERA LOOK ANGLES
,
4. AS POINTED OUT IN REPORT NUMBER II, A POLARIZER IS NELPFU
ON A HAZY DAY, BUT THE DEGREE OF IMPROVEMENT IS SLIGHT. POLARIZ
5_ a POLARIZER USED ON A CAMERA LOOKING AWAY FROM THE: suN, n
t CAMERA FLYING PERPENDICULAR TO~THE SUN'S AZIMUTH, A WIDE DENSITY
':> VARIATION ACROSS THE FORMAT WOULD PROBABLY EXIST._ _ _ wwA _~
? IAS
- - - - ,b~A-&Y4
SOMETIMES POLARIZED TO THE EXTENT THAT THE POLARIZING FILTER WILL
CANCEL OUT OR OBSCURE IMAGERY.
7. ~ F THESE CONCLUSIONS, IT WOULD SEEM APPARENT THAT
PAGE 31 ? S E C R E T
MUCH M G IN THIS FIELD IS NEEDED. THE FEW REPORTS THAT
ARE AVAILABLE ARE ONLY APPLICABLE TO A GIVEN CIRCUMSTANCE.
S E C R E T
-END OF MSG-
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VDL1u~UC. n~:.~.ina.. ~ ~?~-~--????? ??- REPORTS ON
1. AS PER YOUR REQUEST, THE
POLARIZATION OF OBLIQUE AERIAL PHOTOGRAPHY AND THE ACCOMPANYING
SAMPLES WERE REVIEWED AND THE FOLLOWING CONCLUSIONS HAVE BEEN REACHED:
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WITH T~~T
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Sanitized Copy Approved for Release 2010/06/18 :CIA-RDP78B04549A001100020048-2