Magenta edge tinging at high ISO and a possible solution...

Started Aug 17, 2009 | Discussions thread
GordonBGood Veteran Member • Posts: 6,308
Re: Magenta edge tinging at high ISO and a possible solution...

jamesm007 wrote:

Yes the K20D has it fairly strong at iso3200 as well (nothing like iso6400) under the right conditions and perhaps a little lower. Can you offer a user adjustable strength slider? I know you really love this more work. Or is it necessary?

James, a strength slider isn't really necessary as the correction as determined by Dominique is based on the improperly corrected masked black offset determination photosites. These should be at zero other than for some random noise, but instead they have an average positive level that varies apparently linearly over the width and height of the image. The correction consists of determining the trend lines associated with this offset drift and subtracting these offsets from the rows and columns of all the exposed raw image data.

The correction applied probably will improve images down to about ISO 800 or so, as it looks from the K20D samples that I have that the offset error is about 10 levels out of the full 12-bit range of 4096 levels and the error will vary linearly with ISO sensitivity; however, you would likely never notice the fringing at ISO 800 and it would be pretty slight at ISO 1600.

Regards, GordonBGood

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