« on: July 15, 2013, 09:09:43 AM »
This is a confusing topic because the term "1.6 x crop" is a bit confusing to some. You hear that when you mount a 100mm lens on an APS-C camera it behaves like a 160MM lens on a FF camera. Really, what it means is that the field of view is the same as if you had a 160m lens on a
cropFF camera, but it does not mean you have a 160mm lens.
The lens remains a 100mm lens. It's optical qualities do not change, it's depth of field does not change, it's aperture does not change. When you mount that lens on an APS-C camera you are using a sensor that will only sample the center 40% of the image ( 1/(1.6^2)).
If you were to use a FF sensor with 46Mpixels that was built with the same technology as an 18Mpixel APS-C sensor, the center part of the FF image capture would be ABSOLUTELY identical to that of the APS-C image.
So, sensor size has no effect on DOF or aperture.
Good explanation, with wrong conclusion. Using similar logic we can say that lens-sensor combo has no effect on DoF as well, only subject (scene) size and distance matters. DoF is not a constant describing the lens or the sensor, but it is described by the combination + distance.