We'd also get depth of field that looks about the same¹ as if we had used f/4.5 with the 80mm lens on the FF camera.

We would get a field of view that would be equivalent to using an 80mm lens on a FF camera.

1.6X wider and 1.6X taller) sensor.įor example, if we use a 50mm lens at f/2.8 on our Canon APS-C camera with a crop factor of 1.6X, then: When we use a 1.6X cropped sensor, the change in depth of field is very close to the change in depth of field that would be the case if we used a 1.6X longer lens with a 1.6X higher f-number on a FF ( i.e. The difference is that when we take the image collected using a smaller sensor and enlarge it to be viewed at the same display size as an image taken with the same focal length lens using a larger sensor, we must enlarge the image from the smaller sensor more. So an f/2.8 entrance pupil is still 17.9mm wide for that 50mm lens. Remember, our focal length didn't really change, only the angle of view actually changed due to using a smaller sensor. With regard to 'aperture', what does change is depth of field (DoF) or depth of focus (DoF). 'close enough for government - or photographic - work') what we get when we multiply 2.8 by our 1.6X conversion factor (and, of course, 1.6X is the same ratio between 50mm and 80mm). If our lens is 80mm and has a diameter of 17.9mm, though, that gives us f/4.5. If our lens is 80mm, f/2.8 is an aperture 28.6mm in diameter. If our lens is 50mm, f/2.8 has an aperture of 17.9mm. But strictly speaking, the aperture is a diameter of an opening, not the ratio of that diameter to the focal length. The lens focal length divided by the diameter of the aperture, more properly called the entrance pupil, is the f-number that we often call the 'aperture'. When we say we used an aperture of f/2.8, for instance, what we're really saying is we used an aperture that was 1/2.8 in diameter compared to the lens' focal length. It's used to determine how much light per unit area falls on a sensor or film over a specific time period (the exposure time or 'shutter speed').

This is because the f-number is a dimensionless ratio. With regard to 'aperture', what doesn't change is exposure. We often associate a specific angle of view with a particular focal length and film size, and when we say using a crop sensor 'changes' the focal length what we are really saying is that using a crop sensor changes the angle of view as compared to using the same focal length with a 36x24 mm piece of film or a 'full frame' sensor that is essentially the same size as the 135 format (i.e. (We are assuming neither the focal length, f-number, the camera position, nor the focus distance to our subject changes - only the size of our camera's sensor.) What does change is the angle of view and the depth of field, but not the exposure. This is why each manufacturer offers a range of lenses designed for its format.Neither the focal length of the lens nor the aperture of the lens change if we change the size of the sensor.

Each variant results in a slightly different angle of view from lenses at the same focal length and overall a much narrower angle of view compared to 35 mm film. Sensor sizes range from 20.7×13.8 mm to 28.7×19.1 mm, but are typically 22.3×14.9 mm for Canon and 23.5×15.6 mm for other manufacturers. Because of this, devices with APS-C sensors are known as 'cropped frame,' especially when used in connection with lens mounts that are also used with sensors the size of 35 mm film: only part of the image produced by the lens is captured by the APS-C size sensor. Īll APS-C variants are considerably smaller than 35 mm standard film which measures 36×24 mm. Such sensors exist in many different variants depending on the manufacturer and camera model. APS-C size sensors are also used in a few digital rangefinders. Sensors approximating these dimensions are used in many digital single-lens reflex cameras (DSLRs), mirrorless interchangeable-lens cameras (MILCs), and a few large-sensor live-preview digital cameras. Image sensor format Drawing showing the relative sizes of sensors used in most current digital cameras.

Full frame to aps c lens conversion