There are countless videos and forum threads discussing and debating about the principles of crop factor, depth of field, and sensor size. However if you are the type to geek out over the math and physics of photography then this is the video for you. This is no simple examination, at 35 minutes long it requires some advanced knowledge on camera sensors.
Blake Evans goes deep into the differences between full frame and crop sensors and why there is so much confusion. With diagrams, examples and detailed explanations Evans gives you everything you need to get a true equivalent image from the variety of sensors.
Behind all the details and diagrams is Evans simple “recipe” for getting true equivalence across all sensors. This equivalence as he demonstrates is not just equal field of view or exposure but in fact equal everything: lens, aperture, distance, and depth of field. This is done by applying the crop factor to the focal length, aperture and ISO.
FOCAL LENGTH = Apply Crop Factor
APERTURE = Apply Crop Factor
ISO = Apply Crop Factor²
Although this formula seems simple and Evans provides more than enough to demonstrate the evidence behind his statements if you take a look at the comments on the video this is still a hotly debated subject. I highly recommend trying to make it through the full 35 minutes. It's clear from the video and comments that there is a lot of confusion surrounding this topic but for the vast majority of photographers this might just be useful with all the options offered today in sensors.
[via No Film School]