Zero Image Zero 135 Instruction Manual page 8

If you don't want to use a light meter, the following guide may
help: 1-3 seconds under bright sunlight, 4-20 seconds for shade;
4-10 minutes for cloudy, for indoor or night scene, use 15-45
minutes or more. These estimated exposure times are based on
ASA100 film.
Reciprocity Corrections
If the exposure time is shorter than 1/10,000 seconds or longer
than 1 second, it is necessary to calculate and adjust for
reciprocity failure.
Exposure time indicated by
Exposure scale
1 second (or over)
5 seconds (or over)
50 seconds (or over)
Note: 1. All information mentioned above is based on ASA 100 film
speed.
2. Some practice will be required to relate the times given in
this chart to your particular camera and film. Keep a careful
record of the light conditions and the exposure times for
every photograph you take, so that future adjustments may
be made easily.
Compensation
x2
x5
x12
6
Exposure
2 seconds
25 seconds
600 sec or 10 min.