Reading the mm on a lens or the f-stop on the barrel of the lens may look the same on all cameras, but using the same value on cameras with different sensor sizes will provide different results. First, the f-stops do not let the same amount of light into the camera; a Fujifilm APSC camera with an f-stop of 1.4 is similar to f2 on a Sony full-frame camera. A f-2.8 lens on a GFX medium format camera is identical to f-2.2 on a full-frame camera. Second, a 50mm lens on a full frame has a similar field of view to a 35mm APSC lens or a 63mm lens on a medium format camera. The other difference is as sensor sizes get smaller, there are more noise issues. The larger the sensor, the larger the lens; the larger the lens, the more light it can gather.
f/stop Equivalents
The following chart shows that an APSC sensor camera with a 1.4 f-stop is equivalent to f2 on a full-frame camera. However, on a medium format sensor, an f2 lens would be comparable to f-1.6 on a full-frame camera or.
Sensor Sizes, Crop Factor and Lens Equivalency
In the following chart, the key column is the first blue column labelled FF, as in most instances, people compare different sensor sizes by comparing them to Full Frame equivalents. To get the full frame equivalent of a Medium format lens that is 110mm, according to this column in the chart, you would multiply 110 by .79. So a medium format 110mm lens is equivalent to an 85mm (86.9) full frame lens.
Sensor Size Comparison
