I've seen the Canon 5D Mark III, Nikon D750 and A7R before. The sensor placement of the Nikon and Canon reveals the whole sensor if you look "down" the mount on the camera. On the A7r though the corners of the full frame are hidden, from what I can tell, under the mount.


Does this actually impact image quality or am I noticing too much?


Nikon D750 Canon 5DIII A7R

  • true, sony mount is relatively narrow compared to the others, but your photos of nikon and canon don't reveal the sensor size - what we can see there is the matte screen reflected in the mirror (and the sensor is hidden behind).
    – szulat
    Nov 23, 2015 at 15:13

1 Answer 1


All three cameras have the same 36mm x 24mm sized image sensor.

The Sony A7R is a "MirrorLess" camera and when the lens is removed you can see the image sensor.

The Canon 5D Mk III and Nikon D750 are DSLR's and what you normally see is the mirror and viewfinder reflection.

If you flip up the mirror and open the shutter on the Canon or Nikon (as when cleaning the image sensor) they all look pretty much the same. The Nikon actually has the smallest diameter mount but that has no effect on image quality.

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  • Can you explain why it has no effect on image quality? I presume it effects vignetting? Nov 24, 2015 at 18:02
  • 1
    Nikon's smaller mount has no effect on the final image because the lenses are designed to deal with the smaller opening and the image is able to cover the entire sensor. Canon went with a larger mount in 1989 when it went to Auto Focus and and gives more latitude in lens design. Nikon stuck with the older smaller mount of the Manual Focus lenses for commonality but has to deal with additional constraints in lens design. Nov 24, 2015 at 19:42
  • Thanks for the reply. I guess at the end of the day, if the lens and body are well designed, it will do it's job. Nov 25, 2015 at 0:41

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