DEAR DICK:

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A000700010013-0
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 2
• Document Creation Date: December 28, 2016
• Document Release Date: March 29, 2002
• Sequence Number: 13
• Content Type: LETTER

Approved For Release 2002/06/17 : CIA-RDP78BO4747A00070001
LEGIB
Under the subtask entitled, "Refinement of Techniques", a recent
investigation was performed to ascertain the qualities that an original
negative must possess in order to properly simulate the parameters of
the mission material by the GEMS technique. The key factor associated
with the original negative is its processing. If it is desired to
maintain both an adequate scene density range and high resolution in
the simulation process, it is essential that the original negative be
photographically processed to a gamma of unity.
The justification for the unity gamma processing can be described
best by explaining the inadequacies of GEMS generated from higher gamma
originals. The simulation procedure requires that a positive master
transparency be generated with a cascaded gamma of unity. For an original
negative with a gamma of 2.3,: it is therefore necessary to process the
master transparency to a gamma of 0.43. In the master reduction process,
the 2.8 density range of the negative material is compressed to 0.84
density units. When these positive master transparencies are used to
generate negative GEM PHOTOGRAPHS with a gamma of 2.3, the maximum density
range that can be achieved is 1.45 density units. Under normal processing
conditions for a gamma of 2.3 and with the proper exposure or scene
illuminance, the mission material has a 2.6 to 2.8 density range capability.
When using a high gamma original negative, nothing can be done to
match the density range of the GEM PHOTOGRAPHS with the mission material
without detrimentally influencing some other photographic parameter in the
simulation procedure. The low gamma processing of the master transparencies
also limits the resolution capabilities of the GEMS.
Ideally, negative material, processed to a gamma of 1.0 and possessing
a maximum density of 1.5 to 1.6, should be used when generating the master
transparencies. We strongly urge that such negative material be obtained
from the system designated as "B" Material along with a sensitometric step
tablet. (All other parameters should be the same as for the material
obtained previously.) The material is required by mid-December, at the
latest, if it is to be used in generating the matrix GEMS. I feel that
it is our duty to inform you that if such material is not employed in
generating the masters, there is a very high probability that the mission
material cannot be satisfactorily simulated.
Regards,
STATINTL
Declass Review by NIMA/DOD
Approved For Release 2002/06/17 : CIA-RDP78BO4747A000700010013-0
 r 7 App oved or e702/06/17 : CIA-RDP78B04747A000'700010013-0
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