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I have lenses from a Canon EOS rebel Xs film camera: 28-80mm f/4-5.6 II (diameter 58mm) and a Sigma 100-300mm f/4.5-6.7. I am thinking to buy a Canon Digital 40D and use these lenses. Will those lenses be compatible with a digital camera?

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I've read reports, especially around the time that the 30D came out, that some cameras' auto-focusing could be bit off with older EF lenses, and could be improved if the lenses were sent back to Canon to be recalibrated. – Mark Plotnick Oct 20 '13 at 16:17
@MarkPlotnick With the Canon system the fine calibration is done to the camera body, not to the lens. Even bodies that don't feature user accessible AFMA can be adjusted at the factory. The issue when digital bodies (such as the 30D) first began replacing film bodies was more about the ability to pixel peep with digital. And since a digital sensor is almost perfectly flat compared to a frame of film, slight focus inconsistencies are much more detectable with digital cameras. – Michael Clark Apr 15 '15 at 2:24

Yes, they are theoretically compatible (third-party lenses sometimes have problems), as you were told already. The camera will focus and meter properly with these lenses. As @Stan also mentioned, they wont perform up to par with modern lenses.

The key difference is that the Canon EOS 40D has an APS-C sensor which is smaller than 35mm film by a linear factor of 1.6X. This means that the field-of-view you see on the 40D will NOT be the same as on the film camera. For your lenses that means:

  • The 28-80mm will give you the same field of view as a 45-128mm lens would on the film camera.
  • The 100-300mm will give you the same field of view as a 160-480mm.

So while they are compatible, you will lose wide-angle coverage. That would require a lens starting at 17mm or so. One a full-frame DSLR like the EOS 6D, 5D (any Mark) or 1D X (or previous 1Ds series), the field-of-view would be the same because those cameras do not have a crop-factor.

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Just to be clear, the difference in field of view has nothing to do with the age of the lens -- any EF lens will have the same difference between full frame and APS-C sensors. – Caleb Oct 21 '13 at 2:26

Yes, those lenses will be compatible. The EOS Rebel uses the same EF mount lenses as the EOS digital SLRs. They might not perform as well as more recent designs (focus will be slower, and the lenses will be more prone to flare than ones coated for use on digital cameras), but they will work just fine.

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I had to downvote because modern coating has absolutely nothing to do with the camera behind being digital or film. – Agent_L Jun 7 at 17:44

The Canon lens will work, no questions asked. The Sigma may or may not work, if it does not it is due to electronic incompatibility... Sigma has not licensed the Canon EF communications protocol that makes the lens and camera body talk to each other, but has reverse-engineered it instead. This means that while a Sigma lens works on camera A it may not necessarily work on camera B because camera B uses bits of the protocol that were inactive in camera A and that Sigma did not know existed. There has been a number of issues with old Sigma lenses on "newer" (post-Canon 1D mark nothing, IIRC) Canon bodies. Sigma did offer free software upgrades ("re-chipping") of such lenses back in the day but I don't know if they still do.

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