Stephan’s Blog

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Posts Tagged ‘black dots

EOS 5D Mark II: The ‘Black Dot’ Phenomenon

with 15 comments

My noise behavior photos have stirred quite some interest. I’ve uploaded these photos to my new blog on the day the camera was released to the public.

After pixel peeping, someone has discovered black dots right next to blown-outs. If they show, then they always appear a few pixels to the right of the blown-outs in landscape-oriented photos. The higher the ISO the more pronounced the effect appears to be.

Below is a crop of the ISO 3200 image that I’ve shown in my noise behavior post. You can clearly see these ‘black holes’. Some notes:

  • To the best of my knowledge, I turned off all in-camera processing such as picture style and noise reduction. I wanted to show results as close to the RAW file as possible.
  • I turned off all processing in ACR5.2 (Photoshop CS4 trial version), e.g. no ‘Recovery’ or ‘Blacks’ adjustments, no sharpening or noise reduction, no adjustments of curves or vignetting.
  • The same black dots appear in the results I get from the version of DPP that comes along with the EOS 5D Mark II.
  • To post it on my blog, I converted the results to JPG with the least amount of compression (setting 12 in Photoshop).
  • The crop below has been blown up by a factor of about 2.5 to clearly show the phenomenon.
_mg_0166_crop_copyright_stephan_hoerold

Black dots in a night shot taken at ISO 3200

So what’s the problem? I don’t know but I hope it can be fixed in firmware. The sensor is supposedly identical to the one used in the Canon EOS 1Ds Mark III which doesn’t appear to show this behavior. Although the optics in front of the sensor has been changed to reduce the micro lens gap, I can’t imagine this is causing this phenomenon.

Another indicator that it is not a sensor issue is a shot taken at ISO 50. The same areas that show black dots in the ISO 3200 shot appear more like some sort of flare. I wonder if these flares are caused by the lens optics or by the sensor optics.

_mg_0160_crop_copyright_stephan_hoerold

Same area at ISO 50

I’d like to contact a Canon representative who’s close to optics or firmware development, but don’t know who to get in touch with. So if you can give me a name, please post a comment. I will not publish it to protect the representative’s email address.

I should note that it is not only my camera that shows this problem. There is already a variety of examples shown on various other sites.

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Written by glubsch

December 7, 2008 at 10:06 am