The Darkroom Automation exposure system is the marriage of the Zone System as applied to prints and the EV system taken to it's logical conclusion.

The system is, for now, probably the limit of what can be done in tone control using conventional darkroom methods.

Like the Zone system most practitioners cherry pick parts of the system to get results that are sufficient for the intended use of the print. Like the Zone system using all of it produces stunning prints.

Better prints that match your vision

Faster results with few or no test prints

Cheaper working with less wasted paper, less wasted chemistry and less wasted time.

The fundamental principle of photographic exposure is:

        exposure = light intensity * time

and any combination of intensity and time that results in the same total exposure will produce the same density on a negative or tone on a print.

If light intensity and time are both measured in stops, a logarithmic quantity, then:

        exposure = light intensity (stops) + time (stops)

Darkroom Automation’s f-Stop timer, and timing charts, relate time as measured in stops and seconds as:

The meter displays intensity in stops, related to intensity as:

(The meters are calibrated to a high stability precision light source and not actual RC paper, the times above are approximate.)

Adding the meter reading and the timer setting gives the total exposure. Using MGIV RC as an example, any meter reading and timer setting that sum to 9.9 will produce a maximum black.

In Darkroom Automation's parlance 9.9 is the 'paper speed' for Zone 0 (maximum black) for Ilford MGIV RC and a #2 contrast filter. As an example the exposure speed for an 18% gray is 7.3 and any combination of meter reading and timer setting that adds to 7.3 will produce an 18% gray on the paper.

Darkroom automation publishes paper speeds for popular papers. The charts indicate the exposure required to produce a given tone on a given grade of paper. They also show the difference in paper speed exposure for common tone pairs for determining paper grade.

Paper speed charts, spread sheets that generate charts from test results, HD and zone/exposure graphs, stop-timing tables, f-stop timing dials for Gra-Lab timers, and more are available in the website's Support Directory

Charts are not a necessity: A test print of tones with the required exposure written on the print works very well.

Using this system with Darkroom Automation's Precision Enlarging Meter is covered in the Meter FAQ.