The DARKROOM COOKBOOK, Third Edition

Formulas
FILM DEVELOPERS
Development Time
For some formulas, such as Kodak D-76, time/temperature data is readily available from Kodak.
Where possible I have included a range of times. Other formulas will have to have times
determined for your working methods. When in doubt follow Gordon Hutching’s maxim, “It’s
always 12 minutes.”
When a fi lm developing-time range is given it is for fi lms rated by the manufacturer
between ISO 100 and ISO 320, unless otherwise stated. To choose a starting time, use
this rough rule of thumb: For fi lms rated between ISO 100 and ISO 320, use a time in the middle
of the range. For fi lms rated from ISO 12 to ISO 80, decrease the development time from
the midpoint by 25%. For fi lms rated higher than ISO 320, increase the time from the midpoint
by 25%.
EXAMPLE: Suppose a developing formula recommends using between 10 and 14 minutes.
With an ISO 125 fi lm, start by developing a test roll for 12 minutes. With an ISO 50 fi lm,
develop for 25% less, or 9 minutes. With an ISO 400 fi lm, increase by 25% to 15 minutes. This
is a rough rule, and you may fi nd that it is too much or too little. That is why an initial test roll
or two is recommended.
If you routinely overexpose fi lm by rating it at a lower EI (e.g., Tri-X rated at EI 250
instead of the manufacturer’s recommended ISO 400), try developing it at the time indicated
for the new EI. In the example just given, that would mean developing Tri-X at 12 minutes, as
you would for any fi lm rated between ISO 100 and ISO 320. With most developers a variation
of one minute on either side of full development will not seriously affect the results.
Testing
Take some fi lm, walk down the street, and expose it to a range of subjects. Try to include textured
whites (painted white buildings) and some deep shadows. Keep careful notes. In the
darkroom, cut the test roll into two, three, or four equal strips. Develop each strip for a different
time. Give at least a 10% increase or decrease in time from your best guess starting time.
Round the time off to the nearest 30 seconds. When in doubt about what time to start with,
do what I do—start with 9 minutes for slow fi lms, 12 minutes for medium speed fi lms, and
15 minutes for fast fi lms. These times will probably be too much or too little which is why it
is important to use a test roll.