This web application helps you find the 35mm/full-frame equivalent of a focal length in a different sensor or film format.
Like many photographers, you might be familiar with focal lengths in the 35mm/full-frame image format and the field of view that these focal lengths represent (e.g., 24 mm = wide angle, 50 mm = “normal,” etc.). However, different formats require different focal lengths to produce an equivalent field of view.
With this application, you can look up and calculate these focal lengths and their 35mm equivalents.
The equivalent focal lengths are calculated based on the diagonal of each imaging format.
For example:
35mm format diagonal ≈ 43.3 mm.
APS-C format diagonal ≈ 28.8 mm
Diagonal ratio: 43.3 mm / 28.8 mm ≈ 1.5
50 mm in APS-C ≈ 75 mm in 35mm/full-frame format, because 50 mm *
1.5 = 75 mm.
Using a diagonal-based calculation (instead of width or height-based) is not ideal when the aspect ratios of the compared formats vary greatly, as is the case, for example, when comparing full-frame with its 3:2 aspect ratio to a 6x6 square format. However, this still seems to be the most popular and useful method for making this comparison.