Reciprocity failure question...

[Andrew O'Neill]

Which film are you using?

[Heroique]

Reciprocity failure with black and white requires longer exposure correct?

How do you determine how much longer time is needed?

Here’s a general “starter’s chart” for times under 2 minutes for traditional b/w films (not T-grain), until one becomes more familiar w/ personal equipment & film, darkroom processing habits (such as “N-1” or “N-2”), and preferred results. As you learn more, adjust to your taste:

• Metered 2 sec. – use 4 sec (2x)
• 4 sec – use 12 sec (3x)
• 8 sec – use 32 sec (4x)
• 15 sec – use 75 sec (5x)
• 30 sec – use 3 min (6x)
• 60 sec – use 7 min (7x)
• 120 sec – use 16 min (8x)

Over time, my personal reciprocity charts for various films depart more and more from the chart above, and from manufacturing suggestions, but not by a very significant amount.

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Side note:
“This is commonly known as ‘failure of the reciprocity law’,” AA says in his book, The Negative, “but I prefer the term reciprocity effect as it is not actually a ‘failure.’ ”