I've downloaded a sample RAW image from the brand new compact superzoom camera Sony DSC-RX10 Mark IV and opened in RAW Therapee 5.2.
As the camera is very new, the program doesn't know how to handle it and the result looks like this:

DSC RX10M4 from RAW

What do those black corners mean? Is the wide end of the lens (focal length: 8.8mm, 35mm equivalent: 24.0mm), f/5.6 unable cover the sensor and the corners need to be restored/computed from remaining pixels? It's not just a vignetting, is it?

I thought this would happen only if you attach a DX lens to an FX body etc.
Do all compact cameras with zoom lenses behave like this?

Note 1: I've found how to correct it with a lens distortion slider in RAW Therapee manually.
Note 2: It doesn't happen with RAWs taken with longer focal distances.

Sample image taken from this DPReview gallery (image 29/33). Direct file links don't work.

  • \$\begingroup\$ Which size does RT report? Is it the same size as in the camera spec? Or is it a bit more in each dimension? \$\endgroup\$
    – Gerhardh
    Sep 15, 2017 at 7:54
  • \$\begingroup\$ Camera JPEG: 5472x3648, size in RT: 5488x3664. Slightly bigger but not enough to cause a vignetting like this. \$\endgroup\$ Sep 15, 2017 at 18:04
  • \$\begingroup\$ I have the same problem on my a6000 with sel18200LE.but black corners appears just on 18mm. \$\endgroup\$
    – Remi
    Feb 1, 2018 at 20:59

1 Answer 1


Yes, most likely the lens doesn't cover the whole sensor at the wide end - but correcting for barrel distortion (which happens automatically when shooting JPEG) moves the vignetted corners outside the corrected image area. It's a trick employed to shave just a tiny bit more off the size of the lens.

  • \$\begingroup\$ so you are saying, Sony ships camera that has such noticeable vignetting before distortion correction is applied? \$\endgroup\$ Sep 15, 2017 at 1:10
  • \$\begingroup\$ @aaaaaa Apparently so. \$\endgroup\$
    – Michael C
    Sep 15, 2017 at 1:16
  • 1
    \$\begingroup\$ @aaaaaa Definitely so. It just happens that I'm working on a lensfun correction profile for the RX10 MkIII right now, and it exhibits the same behavior (it sounds like the Mk IV uses the same lens... I hope!). I've seen this at the wide end of other fixed-lens cameras, even some wide primes. Manufacturers take maximum advantage of the lens being a known quantity. \$\endgroup\$ Sep 15, 2017 at 4:17

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