The Exposure Calculator allows us to determine the correct exposure of a frame with a single attempt.

How to use it:
1. We place the calculator on the frame like a normal film.

2. We think an exposure time that we expect is correct.
For example: 8 minutes.

3. We double this time and expose the frame.
So: 2×8 minutes = 16 minutes.

4. We normally develop the frame under water.

5. The calculator is made up of 5 areas with different shades of gray: we will notice that only one of these areas will be correctly exposed.
In other areas, however, the emulsion will dissolve excessively, or we will struggle to open the lines.

6. We then read the number written at the bottom in the correctly exposed area.
This is the coefficient by which we must multiply the time used (in our case, 16 minutes) to obtain the correct exposure time.

Example:
the correctly developed area bears the writing T x 0.5.
Then the correct frame exposure time will be 16 minutes x 0.5 = 8 minutes

The calculator can be reused over and over again.