Adjust a metered exposure for bellows extension and reciprocity so the real shutter time is easier to set.
Recommended exposure
--
Enter the metered exposure, focal length, bellows extension, and reciprocity profile to estimate a corrected shutter time.
Tap an example to prefill the calculator with sample values.
Close-focus B&W portrait
Bellows extension plus mild reciprocity
A longer extension nearly doubles the exposure before the film’s reciprocity behavior adds a little more time on top.
Result: Bellows compensation gets the exposure close to two seconds, and reciprocity nudges it a bit higher.
Macro color setup
Long exposure with a stronger reciprocity penalty
Bellows extension and reciprocity stack quickly on longer metered exposures, which is why slide or color work can jump into much longer real times.
Result: A four-second meter reading can turn into a much longer real exposure once both corrections are applied.
Studio copy work
No reciprocity penalty and no extension lift
When extension stays near the focal length and the film stock behaves well, the meter reading remains a solid guide.
Result: With no extra bellows factor and negligible reciprocity penalty, the metered exposure stands.