If you really like to nerd out over gear, then this is your moment. Blake Evans tackles the myths, misconceptions, and general confusion surrounding depth of field, crop factor, and the differences between full frame and crop sensors. In this very detailed video, as well as in his equally detailed write-up in PetaPixel, he offers illustrations that explain these principles in depth to show you what you need in order to get a true equivalent image from different sized sensors.
As you might've noticed, this video isn't for the faint of heart. It's geared toward professionals who not only have some advanced knowledge of crop factor and camera sensors, but who also want to fully understand crop factor equivalence, as well as how speed boosters work.
As Evans explains, the "recipe" for crop factor equivalence is pretty straightforward; it's the reasons why you need to use it that some have a hard time understanding. The idea here is that it's not just about getting the same field of view or exposure between different sensor sizes, it's also about getting true equivalence: same lens, aperture, distance, depth of field, everything. To do this, you should not only be applying your crop factor to your lens' focal length, but to your aperture and ISO as well. When you do it right, not only will your field of view and depth of field be equal, but your noise levels will be, too.
Evans' recipe for crop factor equivalence
Notice how the "bokeh balls" on the car are the same size.
Source: PetaPixel
