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Tag Archives: lenses

The 5×7 format is a bit of an odd duck. It’s a surprising amount larger than 4×5, in terms of film area (and makes for a good contact print size), and it’s substantially smaller (and thus easier to carry around; cheaper to purchase) than 8×10. 8×10 is a great choice when gigapixels are required — you can blow up an 8×10 negative to billboard proportions and it’s still quite clean.

However, I have so much experience with 35mm sized lenses that I found myself getting lost thinking about which lens length in 5×7 is equivalent to what length in 35mm. I know, it’s a horrible crutch, but I instinctively know that (for instance) 85-100mm is the length of lens I want for shooting portraits in 35mm.

So, to help get it right in my head, I just sat down and calculated out the actual lens to film relationships between a few different lenses. This of course as I ponder whether I want to find more 5×7 lenses (they’re shockingly expensive for being moribund technology).

Here, then, are the numbers I just worked up, for posterity.

35mm Film (43.27mm diagonal)
Lens length % of film diag
24mm 55.4%
50mm 115%
85mm 196.4%
100mm 231%
5×7 Film (222mm diagonal)
Lens length % of film diag
120mm 54%
210mm 94.6%
360mm 162%
500mm 225.2%