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This question already has an answer here:

I am choosing a camera and lens.

I want to buy a Canon EOS 650D, as this camera seems to be a good point of entry into the world of SLR.

My question is in the following:

The EOS 650D has a cropped sensor, so as I understand if I use Canon 50mm f/1.8 lens, the behavior will be quite different on a smaller sensor in comparison to full-frame sensor.

What is the relation between cameras sensor size and lens focal length?

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marked as duplicate by MikeW, Matt Grum, Paul Cezanne, John Cavan, mattdm Mar 31 '13 at 13:28

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Hi Alex. Basically with a smaller sensor, any lens is effectively 1.5-1.6 times what you'd get on a full frame. So 50mm on a 650D is like a 75-80mm lens on a full frame camera. Have a look at these: focal length and crop factor and Does my crop sensor camera actually turn my lenses into a longer focal length? – MikeW Mar 31 '13 at 7:13
And this - How can I get the same image with the same 50mm lens on both FF and APS-C? - Those links should explain how it all works. Basically a 35mm lens on a 650D is similar to a 50mm lens on full frame. 50mm is stil fine on a crop sensor, but if you're say indoors, you may find you don't have as much working room as you would with full frame – MikeW Mar 31 '13 at 7:14
@MikeW Thanks for useful links – Alex Mar 31 '13 at 7:52
up vote 3 down vote accepted

The 650D has a "crop factor" of 1.6 so a 50mm will have about the same field of view of 50*1.6=80mm on a full frame.

This does not change the lens's focal length (or any other optical property) you get a "zoom in" effect because you only looking at the center of the image projected by the lens, that center part of the image is exactly what you would see with a full frame camera in the same exact situation if you cropped the picture in post processing and kept only the center area.

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Thanks, it clarifies a lot. – Alex Mar 31 '13 at 7:56

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