How to read a development table

The development table is the most useful page in a film's datasheet, and it packs a lot into a small grid. This is how I read one, using Ilford's layout.

Columns are meter settings

Across the top you'll see EI values such as 200/24, 400/27, 800/30. The first number is the speed you set on your meter or camera; the second is the same speed in DIN degrees. Choose the column for the speed you shot at. Box speed is not always the "normal" column: on Ilford's Delta 400 sheet the bold times, which give their normal contrast, sit at EI 500 for DD-X and Microphen.

Dilutions

1+4 means one part concentrate plus four parts water, so five parts in total. Kodak writes the same thing as 1:4. "Stock" means the developer as mixed from the packet, used straight. HC-110 has letter dilutions: Dilution B is 1+31 from the concentrate. The dilution calculator does the arithmetic for any tank size.

Agitation is part of the time

The times assume a particular agitation. Ilford's, for small spiral tanks: invert the tank four times in the first 10 seconds, then four times in the first 10 seconds of every minute after that. Kodak's small-tank table is also for intermittent agitation.

Two adjustments from the same Ilford notes:

• With continuous agitation (a tray, or some tanks), reduce the time by up to 15%.
• In a rotary processor without a pre-rinse, also reduce by up to 15%. Ilford doesn't recommend a pre-rinse at all; it can cause uneven development.

Other people's developers

Ilford's tables include Kodak, Rodinal and other developers "for your convenience". Their note says those makers can change their products, so treat the times as a general guide. Every sheet ends the same way: if your results are consistently thin or dense, adjust the time until they aren't.

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