Depth Of Field For Different Formats

The amount of light entering a lens at the maximum aperture is the same no matter the size of the sensor. It’s the hole in the lens that lets the light through that counts. So, it is the same, for example, on an APS-C lens with a maximum aperture of f4 and a full frame lens with a maximum aperture of f4. When you think about it, that must be true because f-stops are defined as the amount of light entering a lens.

What does change is the depth of field, and to look at that we have to look at equivalent apertures.

Equivalent Apertures

Equivalent aperture is the aperture value on one sensor format that shows the same depth of field (DoF) and background bluras the aperture on a different sensor.

For example, on a Canon APS-C sensor with a crop factor of 1.6, an f4 aperture would be equivalent to the depth of field on an aperture of f6.4 on a full-frame sensor. To get the answer of f6.4, multiply the aperture by the crop factor. In this example it is 1.6 x f4, which give an equivalent aperture of f6.4

To put it in a more general way, a wide aperture on a full-frame sensor will have a more shallow depth of field than the same aperture on a crop sensor.

Leave a Comment