I always see the reflection on the camera sensor having a little chamfer:

Image from eBay

But the plane in front of the sensor does not have this chamfer, the reflection should be a right angle if it's a mirror:

enter image description here

Where does this chamfer come from?

  • Does the size of this "chamfer" change with your viewing angle? My hypothesis is that it might be the reflection of the rounded mount (the stepped black part behind the metal one). Nov 17, 2022 at 9:13
  • What camera? I presume it's a new mirrorless of some sort. Can you get a better-lit, better focussed, higher res photo?
    – Tetsujin
    Nov 17, 2022 at 11:07

2 Answers 2


It is a shadow of the lens mount due the lighting angle... this image makes it more apparent:

enter image description here

Also note that your blue line is incorrect and the sensor plane begins at (nearer) the red line... the black between those two lines is also shadow.

  • I actually thought it was a thing about the Bayer filter. Now that I see it I feel stupid... Nov 17, 2022 at 16:17

The camera lens projects an image of the outside world on the surface of the light sensitive sensor (or film). For aesthetics, we want this image recorded with a perfectly straight boarder with perfect corners that meet as right angles. Same is true for negative carriers used in an enlarger. From a machining standpoint, we need a knife edge to make this happen. The campher is a neat way to make a knife edge.

  • 2
    I don't see how this relates to the question. Nov 17, 2022 at 9:14

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