To use this BLACK CAT DECODER first select a ULC letter.
A listing of scenes, all requiring the same amount of light,
will be displayed below the chart.
Any film speed (ISO), shutter speed or f-stop may be selected to
display a "good exposure" or under/over exposure.
Play with these settings until you have an appropriate combination.
You may also use this chart to decode a photograph and find its ULC.
This will determine the amount of light that was required
to take the photograph.
Place the ISO, shutter speed and f-stop used to make the exposure,
then select the ULC letter that shows "good exposure".