Generally these tests should be comparative. We should compare for sharpness, grain, contrast, detail in highlights and shadows and off-color highlights or shadows. Prints should be made for best appearance in faces and/or mid-tones and comparative prints should be made to match in these tones. A gray scale included in the scene is helpful.
Comparative tests should be made at the same T-stop. Where an exposure range is made, exposure should be varied with shutter and/or neutral density filters. Clear filters should be used to substitute for neutral densities so the same number of filters are always in place. While the scene used above for lens comparisons can also be used in these tests, it is helpful also to include a high-key and a low-key scene.
A. Testing new film stocks:
Photograph a range of exposures of each scene from the new film and on a known film, from normal to plus and minus 2 lens stops. If forced processing is intended (see below) add a set at minus 3 stops.
B. Testing for off-normal processing (including push processing and flashing):
1. Because there are now three variables — exposure, flash level, and developing time — unless a wide range of combinations is budgeted, it might be well to separate tests for flash and processing, observe the result, and then confine tests of combinations to levels likely to be useful to the desired look. Always compare to a normally exposed and developed scene.
2. Before committing to forced developing, compare with a properly printed, underexposed, normally developed take. In some instances, the only thing forced developing does is raise the printer points.
3. Make a print of a minus-one-stop exposed, "push one" developed take at the same lights as the normally exposed, normally developed take. Comparison will show just what is accomplished by "push-one" developing.
4. If the desired look is obtained but the print is made below printer point 10 or above 40, be cautious because you have limited your latitude.
C. Testing a new emulsion batch for compatibility:
If the new emulsion batch is incompatible, it is more likely to be so in off-normal densities or processes. Follow the same general procedure as in testing a new film; the exposure range need not be as great. If the printer lights vary 2 or 3 points between scenes photographed the same on the two batches of emulsion no harm will be done. If there is a marked difference in shadow or highlight color when faces match, caution is warranted.
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