Bellows Extension Factor: Different Formats

[Darryl Roberts]

Hi

Would the bellows extension factor differ between formats, e.g. 4x5 and 5x7?

 

[wiltw]

Bellows extension relevance is relative to the Focal Length, not the format.

1. If you used 150mm lens and 150mm extension, you get to 1:1, regardless of format
2. If you used 200mm lens and 200mm extension, you get to 1:1, regarless of format

In both #1 and #2, the exposure factor is the same. The difference between #1 and #2 is merely how far from the subject the focal plane is located...600mm in #1, 800mm in #2
And if you changed format, from 135 to 4x5 to 5x7, the only difference would be the size of the area around the subject captured on film...regardless of FL used for 1:1 reproduction. The subject itself would be identically sized (1:1) on all formats, regardless of format the area around the subject would differ, dependent upon format dimensions.