I’ve decided to write a page outlining some common focal lengths for different formats and their equivalency in other formats, it’s something that I never bother to calculate myself but often find that I’ll do a google to get the information, I’ve seen several tables online but wanted to create a page to keep all the information that I need in one place thats easy to get to.
Hopefully this information can help you too.
Since most people have started with or use 35mm or Full Frame I’ll use this as a basis for comparison, most of the world does the same so I’m not going to change anything. In the table below you’ll see common focal lengths on multiple formats with the equivalent focal length and angle of view listed.
Caveat lector: These are not exact angles of view, i’ve had to average them to get the equivalents right and not all manufacturers release lenses in the below focal lengths, the below figures will get you in the ballpark only, for precise results please do your own calculations
|Angle of View (average)||35mm (full frame)||Medium Format 6×4.5||Medium Format 6×6||Medium Format 6×7||4×5 Sheet Film||8×10 Sheet Film|
My above number are calculated for horizontal angle of view, if you would like to do your own calculations then read below for the formula.
For a lens projecting a rectilinear image, the angle of view (α) can be calculated from the chosen dimension (d), and effective focal length (f) as follows:
Consider a 35 mm camera with a lens having a focal length of F = 50 mm. The dimensions of the 35 mm image format are 24 mm (vertically) × 36 mm (horizontal), giving a diagonal of about 43.3 mm.
At infinity focus, f = F, and the angles of view are:
note: The above formula have been sourced from the Wikipedia page on Angle of View, consult there for further information.