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A Concise Explanation of How Crop Factor Affects Both Focal Length AND Aperture


Editor’s Note: Due to some issues with the camera, this video is very shaky at times. It didn’t bother us much, but if you’re easily distracted this video might annoy more than it educates you. You’ve been warned.

If you’re just getting into the world of cameras and lenses, the term “crop factor” and phrases like “this is a 35mm equivalent lens” might still confuse you. Well, that shouldn’t be the case much longer.

The video above offers a clear, concise and simple explanation of crop factor that will hopefully clear all of this up and equip you with some important knowledge that will come in handy the next time you’re shopping for a lens or crop sensor body.

The video was put together by photographer Tony Northrup in response to some comments he’s gotten on his other videos, and although it’s not perfect, it does a great job explaining how crop factor affects not only focal length (read: field of view), but aperture (read: depth of field) as well.


We won’t go into the technical details, since that’s what the video is for, but the TL;DR goes something like this. Using Nikon as an example: a 50mm f/1.4 lens, when attached to a D7100 (1.5x crop factor), will produce about the same image as a 75mm f/2.0 lens attached to a D800 (full-frame camera).

The crop sensor affects your field of view (how close you are to your subject), your depth of field (how thin your focus plane is/how much background blur you’ll get) and the amount of TOTAL light hitting the sensor (same amount of light per square inch of sensor, but less total light because you have less sensor area) and therefore your image quality.

For a more in-depth explanation combined with visuals that really help drive the point home, check out the video at the top. And if you feel you can explain crop factor in an easier to understand way, feel free to drop that explanation in the comments.

(via Reddit)