What the format defines
A sensor of 36 × 24 mm. It is the size against which crop factors and equivalent focal lengths are calculated.
What it does not promise
Full frame says nothing about autofocus, video or resolution on its own.
Lenses
Full-frame lenses, such as the Sony FE 35mm F1.8 or the Canon RF 45mm F1.2, also fit APS-C bodies on the same mount, where they frame more tightly.
Equivalent focal lengths
An equivalent focal length is a calculation: it describes the field of view a lens gives on a full-frame camera. The focal length engraved on the lens never changes.
How to check before buying
Check whether a lens is designed for full frame or for a smaller format before mounting it on a full-frame body.
What people ask before they commit
Why is it called full frame?
Because it matches the full 36 × 24 mm frame of 35 mm film, the reference for focal lengths.
Do I need full frame?
Not for most photography. It helps most in low light and for shallow depth of field, at higher cost and weight.
Can I use APS-C lenses on full frame?
Some bodies crop automatically, as Canon’s RF-S lenses do on full-frame EOS R bodies, at a loss of resolution.
Last reviewed November 2, 2026