thereafter, they can be exposed manually, as desired, by depressing a 
button on the control unit. After the last exposure has been made in the 
jog mode, the switch is returned to the normal 'on' position, whereupon the 
film advances a full frame. 
The recommended film for the CRC-1 is Kodak Tech Pan. This extremely 
fine grain, high contrast film is ideal for applications employing retro- 
reflective targeting. When developed for highest contrast its effective 
film speed may be rated as ASA 200, and the contrast is essentially binary 
(no shades of grey between clear and black). However, as is pointed out 
in Kodak Tech Bits No, 2, 1981, Tech Pan can also be processed in a special 
developer called POTA to have a wide tonal range suitable for general photo- 
graphy. In such applications its ASA rating is from 25 to 50. Tech Pan 
has a dyed gel antihalation backing with a density of 0.1. It thus transmits 
only ten percent of the light from the reseau projectors. When Tech Pan is 
developed to an ASA rating of 100, an exposure of four seconds is required 
for the reseau images. To accomodate various exposure indices for Tech Pan 
and also to accomodate other films with and without antihalation backings, 
the CRC-1 incorporates two rotary switches for selection of film speed. One 
is for the front side of the film and the other is for the back side; both 
have settings for the following ASA film speeds: 5, 10, 25, 50, 100, 200, 
400, 800, 1600. For Tech Pan processed to an ASA rating of 100 the front 
and back settings would be 100 and 10, respectively. 
Tech Pan film on standard 9.5 inch wide reels is presently available 
from Kodak only on special order. The minimum order is 8 rolls and delivery 
is about 90 days. Therefore, as a convenience to its clients, GSI maintains 
a refrigerated inventory from which single rolls are available for immediate 
delivery. 
2.7 OTHER FEATURES OF THE CAMERA 
An auxiliary 35 mm single lens reflex (SLR) camera with motorized film 
transport serves as a viewfinder for the CRC-1. With each of the CRC-1 
lens cones, an SLR lens of appropriate angular field is provided. Aside 
from its use as a viewfinder, the SLR can also be used to take supplementary 
photographs either in synchronism with the CRC-1 or independently. Such 
photographs may be convenient for general documentation or for testing of 
lighting and general exposure. In cases where the CRC-1 is set to record 
only retroreflective targets, the SLR may be useful to record the background 
through use of an appropriate combination of wider aperture, slower shutter 
Speed or faster film. 
With any metric camera using film the utmost care must be taken to 
maintain internal cleanliness in order to prevent dust from lodging between 
film and platen, thereby compromising local flatness. To facilitate clean- 
ing and removal of dust virtually the entire interior of the CRC-1 is coated 
with black Teflon S. 
The platen is coated with Teflon S for two additional reasons. One 
is to reduce friction and prevent scratching when the film is transported 
across the platen. The second is to permit attainment of a higher degree 
of flatness than is normally possible. This stems from the consideration 
that upon being blackened by anodizing a perfectly flat platen of aluminum 
alloy will ordinarily lose a degree of its flatness (changes in excess of 
Sum are not unusual). To restore the original flatness, touch-up lapping 
is necessary, and this sometimes penetrates too far into the anodizing 
which itself is only some 10mm or so thick. On the other hand, when the 
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