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3D-32
The following “duplication tree” illustrates how the
various duplicating microfilms are used to produce the
desired contrast and image polarity of distribution
copies. As an example, 3N is showing 3rd generation
negative-appearing distribution copies.
CN = Camera Negative
LC = Low Contrast
MC = Medium Contrast
HC = High Contrast
1 = 1
st
generation
2 = 2
nd
generation
3 = 3
rd
generation
N = Negative polarity
P = Positive polarity
D = Distribution
Physical properties
* Static-resistant—process-survivable
**Unprocessed
Exposure
The following table indicates value for 1/25-second
tungsten exposures calculated using the formula 45/H,
where H is the exposure in lux-seconds required for a
density of .10 (1.20 for x462 Microfilm) above minimum
density with indicated processing. This number can be
used directly with incident-light meters.
*Recommended processes
Nominal thickness data (mils)
Microfilm Base*
(mils Estar)
Total**
2462, 2468,
2470
4.0 4.2
3468 2.5 2.7
4462, 4468 7.0 7.2
Meter Setting Value*
x462 2.1
x468 0.2
2470 0.12