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Forgive me for my lack of camera knowledge. There's an option for sensor width which zooms the camera in and out. The focal length option seems to do the exact same thing. What is difference and functional purpose of these two similar options? (Note: it's slightly confusing when attempting to match cameras and one is different from the other even when checking to make the focal lengths the same. My confusion prompted this question.)

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Cameras in Blender are made to resemble cameras in real world. The size of the sensor is important when you need to match content created with a real camera with your CG, and that happens really often. Obviously, you might have a hard time to match your camera if you don't enter the correct sensor size. You should search for it online for the specific camera model your content is captured with.

You may also be used to real world cameras so it is easier to reach some desired result if you already know what to expect from some settings or parameters because they match real cameras.

If you have a look, you can see that Blender even comes with lot of presets matching real cameras:

Camera Presets

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  • $\begingroup$ What would you (personally) set your sensor width to if you have no need to utilize it? Having 2 zoom options seems like it could get awkward especially when trying to keep a consistent feeling throughout an animation. Is know its probably up to preference but maybe there might be customary or general rules of thumb relating to the practice. I'm new to this so I'm a little aimless. $\endgroup$ Jan 30 '20 at 10:43
  • $\begingroup$ I don't usually have the need to adjust it and just leave it alone with the default value that happens to be 36 mm. It shouldn't be a preference and you should use focal length for adjusting the zoom. This is how it is in reality as you cannot adjust the size of your sensor in a physical camera. Using sensor size for zooming would probably confuse anyone looking at your files if you need to work in a team or share your work. Unless of course you want to mess with your coworkers, then it's a great thing to do. :D $\endgroup$ Jan 30 '20 at 11:41
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Focal length and sensor width (aperture) are highly misunderstood and abused concepts. The property you are primarily concerned with is actually angle of view or field of view, but Blender does not provide such a camera attribute. Angle of view is the result of combining focal length with sensor width. Ordinarily you will want to adjust your angle of view using focal length since that is most intuitive and consistent with how a real world camera is used. But be aware that focal length means nothing without a known sensor width. A focal length of 50mm in front of a sensor width of 36mm does not provide the same angle of view as it does in front of a sensor width of 24mm. First decide on your sensor size and don't touch it. If you don't know it just accept the default. The only time you need to care about sensor size is if you are integrating real world images with a CG render. Find your desired angle of view using the lens focal length, but don't try to make the numbers mean anything. Just make it look the way you want. If someone says to you, "I want this to look like it does through a 50mm lens", you have to immediately ask them "what is your sensor size?" Otherwise tell them to F*ck off, and ask them how much they want to see in the image (angle of view).

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  • $\begingroup$ Is it necessary to use swear words to explain this subject? $\endgroup$ Mar 15 at 11:00
  • $\begingroup$ Hello :). Not to tread on your nice answer, but Blender of course allows you to use field of view, instead of focal length. $\endgroup$ Mar 19 at 22:59
  • $\begingroup$ Ok, yes there is a Field of View property, but not provided in the default interface. It could be scripted, or displayed with an Add-on. $\endgroup$
    – zippy
    Mar 20 at 2:23
  • $\begingroup$ Oh, wait, I see, the Option menu - Lens Unit displays focal length or field of view....Nevermind. $\endgroup$
    – zippy
    Mar 20 at 2:46

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