In terms of the sensitometric quantities just discussed the general requirements for aerial plates may be listed as follows:

1. Speed

The speed usually connected with the contrast and density required for the exposure times available is about 150 H & D. Faster plates in general have too low contrast, but the highest speed that will give the necessary contrast is desired.

2. Contrast

The contrast capable of development without fog should be from 1.5 to 2. This contrast should be produced by light of daylight quality, and, in orthochromatic and panchromatic plates, with the yellow or orange filters intended to be used with them. This contrast means a gamma infinity approaching 2.5.

3. Speed Of Development

A gamma of nearly 2 should be developed in 23^ minutes at 20 degrees C. in the developers recommended below.

4. Fog. Not Over

25 for this degree of development, and not over .40 for six minutes development.

5. Color Sensitiveness

This should in general be as high as possible. In terms of certain representative filters (described in a subsequent chapter) color sensitiveness should be such that with the white light speed above specified the relative exposures through the filters shall not be greater than as follows: