I am thinking of buying a Canon EF50mmf/1.8STM lens, and was wondering if its compatible for a Canon 600d which has a 58mm dia thread?

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    The filter thread is at the front of the lens. The mount is at the back of the lens. – osullic Nov 3 '17 at 15:20

The thread size is the thin screw threads for the mounting of filters etc to the front of the lens, rather than mounting the lens to the camera.

The lens will fit, (and is probably a good choice), the way to tell is the mount rather than the thread. Canon digital SLRs use either EF or EF-S mounts. The EF mount works on both crop frame (like the 600D) and full frame sensors. Lenses made for the EF-S mount are designed specifically for crop frame sensors. While most third-party EF-S lenses will physically mount onto a full frame camera with no problem, Canon EF-S lenses have a tab that physically prevents mounting them onto full frame bodies. Additionally, a few Canon EF-S wide angle zoom lenses will interfere with the larger mirror in the full frame body. For example, see: Is there a way to use Canon 18-200 EF-s lens on Canon 6D full frame body?

Note that there is another current line of Canon lenses: EF-M, which are specifically designed for Canon M cameras (their mirrorless range). EF-M lenses will not fit the EF or EF-S mount at all.

  • @scottbb Canon EF-S lenses will not mount on FF bodies without modification. There's an extra tab that physically prevents it. Third party APS-C lenses often will mount because they use the straight EF mount. They rarely use the shorter backfocus distance allowed by the smaller APS-C mirrors. – Michael C Nov 4 '17 at 9:07
  • Thanks for the advice. That's good news that it fits. They say that the thread size has been reduced from 55mm to 49mm so filters probably won't fit. Its mainly the mount size I was concerned about, as my 600d has a 58mm dia size, I wanted to make sure that the 50mm STM lens would fit on the camera; am I right in thinking this shouldn't be a problem? Thanks again. – user69624 Nov 6 '17 at 15:01
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    @user69624 you don't need to consider the diameter of the mount end of the lens, only consider the fitting type. Not really sure I understand what you're saying about the thread size being reduced from 55mm to 49mm, unless you've read a review that compares it with a previous version or a different model where the thread size was 55mm. The lens model you've specified is this: store.canon.co.uk/canon-ef-50mm-f-1-8-stm-lens/0570C005 and it has a 49mm thread size (called filter diameter on the link given). Don't forget that the 55mm is the focal length and is'nt related here – laurencemadill Nov 6 '17 at 16:44

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