Chemistry selector

Choose a photographic intention and examine the chemistry class, its limitations and the supporting course evidence.

Compare

Enter your values and calculate. Read the assumptions below before using a result.

Method and assumptions

Start with the visual decision, then test the returned class against the material and your working constraints. Fine grain, strong edge effects and retained shadow speed are different objectives. A comparison is meaningful only when the negatives are brought to a comparable contrast and viewed or printed on a stated basis. More highlight density is not by itself more speed.

The selector returns a class and reasoning, not a formulation, manufacturer ranking or instruction to mix chemicals. The film branches implement the decision table in Part VIII. Fixer, paper-developer and toner branches lead to the now-written Parts XI, XVIII and XX, where material compatibility, capacity, washing and the controls for each operation can be considered in full.

For a first comparison, choose repeatability. Make the control explicit: a named film batch, exposure series, processing volume, agitation pattern and temperature. Reusing a bath introduces a history that fresh one-shot working solution avoids, but one-shot use still has a minimum concentrate and a capacity. Read those limits from the actual product or formula documentation rather than from a label such as fine-grain.

Write the chosen class and the trade-off you expect in your notebook before making the comparison. After processing, state whether the observation tested that trade-off or changed another variable as well. No result from this tool establishes that an arbitrary formulation is safe, stable or appropriate.

Evidence and record

Read the teaching method and its sources. Keep your inputs, the displayed assumptions and the result together; a result detached from its conditions cannot be checked.