Issue with concentric rings on E-M1 Mark II (edited title)

Started Mar 19, 2017 | Discussions thread
pdk42 Contributing Member • Posts: 618
Re: Steps to test for this

Astrotripper wrote:

After more fiddling I arrived at the simplest way to reproduce the problem:

  1. Set the camera to aperture priority and set the aperture wide open.
  2. Set ISO to 200.
  3. Point the camera at a sheet of paper or a wall or any uniform surface, doesn't matter if the focus is spot on or completely off.
  4. Take a few shots with exposure compensation set somewhere in the range of -2 to 03 EV.

The rings are visible on the camera's screen. As far as I can tell, camera settings do not affect the result.

And now that I know exactly what to look for, I can actually see it in live view.

As I already wrote couple of times, I assume the unit I got is defective and will pay a visit to the store tomorrow. But it would still be nice to hear from other users.

Well I tried this on my E-M1ii and found something interesting...

- I can reproduce the rings when reviewing the images on the camera's screen. Happens at about EV -3 or thereabouts. It's quite obvious. I have the camera set to raw only so I'm looking at the low-res embedded JPEG.

- The ORFs in LR latest edition (with formal E-M1ii support) seem almost fine, but if I play around with curves and pushing the exposure I can provoke a slight "bulls-eye" pattern.

I tried the same test with my Pen-F and got a similar result.

I'm guessing it's some sort of posterisation caused by vignetting and low exposure levels. As someone else mentioned it's probably because the exposure is low and uniform so we're getting into the lower levels of the A to D conversion where "quantisation"/stepping becomes more obvious. If I export the images in a low quality (fewer bits) jpeg then the rings become very obvious.

I suspect what we're seeing here is the result of 12-bit processing rather than 14-bit.

EDIT: I suspect the "fix" of shading compensation is merely hiding the issue.  The problem is probably implicit to the way that the image is digitised.

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