Rebel T1i lens registration

Discussion in 'Canon EOS' started by brent_bennett, Oct 13, 2009.

  1. I was told by a friend that the T1i and some other Canon cameras have a shorter lens registration than the standard Canon EOS cameras. I assume then that the EF-S lenses have a shorter backfocus or registration in order to focus properly on the T1i.
    The registration for standard Canon EOS cameras is stated to be 44.00mm. What is the registration for the T1i ?
    Note: I am asking because if the registration is less than 44.00mm, then several lenses (from other manufacturers) could be mounted on this camera with an appropriate adapter that would not work on a 44mm EOS camera.
    Thank you for your response.
  2. It's still 44mm for EF-S compatible cameras.
    However, EF-S lenses are designed to have some parts protruding into the camera body.
  3. Hmmmmm, I'd have to venture a guess that it's still 44mm as the standard EOS "EF" mounts to it as well.
  4. Of course the registration distance is identical, otherwise, as Keith points out, EF lenses would not work on 1.6-factor bodies. Which they do.
    The difference is that on 1.6-factor bodies (with the exception of some early models) the mirror remains closer to the sensor plane as it sweeps up, and so it is possible to design lenses for those bodies that project back further into the body than is possible for FF bodies, as Jonathan has pointed out. Canon have definitely taken advantage of that on some EF-S lenses. But on all EF-S lenses the back cover-plate of the lens projects back far enough to prevent the lens from mounting on a FF body, as a precaution against damage, and those who choose to defeat that protective mechanism do so at their own risk. Since EF-S lenses are designed with an image circle that is only large enough to cover the 1.6-factor frame size, there is not generally much point in trying to mount an EF-S lens on a FF body anyhow.

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