When talking about the differences between full-frame cameras and crop sensors, one of the biggest arguments in favor of full-frame sensors is the ability to produce images with a shallower depth of field. This was always my understanding of the subject as well. But after watching this video, I have seen the error of my ways. As it turns out, if all the variables are the same and the only thing changing is sensor size, the smaller the sensor, the shallower your depth of field.
I'm not going to try and explain all the science and math from the video, because the video does a much better job than I could even attempt. But my biggest takeaway from this video was when thinking about a sensor's crop factor and how that’s used to calculate a lens' equivalent focal length. Most people multiply the crop factor of a sensor by the focal length of a lens in order to get the full frame equivalent. The trick though, is that you need to multiply this crop factor by the focal length as well as the aperture.
The reason why it seems that full-frame cameras have a shallower depth of field has a lot to do with the focus distance needed in comparison to a crop sensor. The example below shows that in order to get the same frame of view on a crop sensor, you need to increase the distance of the subject. This added distance is what increases the depth of field on the crop sensor.
Who here just had their mind blown?