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...

Progress to all: I spent time today researching and eliminating the requirements to add K-7 support as well as researching the best ways to "smudge" the White Balance (WB) which should be done for both the AsShot Neutral DNG tag value and the AsShot WB in the Pentax MakerNotes under the DNGPrivateData DNG tag. I have that pretty well suss'ed.

I temporarily disabled the horizontal correction until I get a chance to see about this godfrog problem and will add it back in with modifications when I understand it a little better.

Limits for the first Beta release will be that I won't yet support PEF format for the K20D, although that will be added before the first production version, and I don't support lossless compression in the source and destination files for the case where the original camera DNG files have been converted to compressed DNG's, which is quite a bit more work to add as I don't have any programming stubs to just copy and paste in from my other work (I haven't yet written this for my own raw converter program as I don't usually use DNG from my own Pentax camera).

godfrog wrote:

Thank you for your reply and your time Gordon.

You're welcome.

I tried using live view, but even pushed to its limit I can not see any of the purple noise. I dont know what processing the live view display has had though, if the back LCD is even good to see the noise (I think it has a high black point), and the image quality is pretty horrendous when zooming live view on the GX-20/K20D.

I think that the LCD monitor doesn't have enough resolution or dynamic range to be able to see this variation in the tones.

I tried downloading Faststone but Im not sure what I need to do to see the masked pixels, the "RAW settings" tab seems very limited, and by default I get no black borders when viewing my RAW files (GX20 DNG -> Adobe compressed DNG with Lightroom, Faststone set to not use the preview JPEG).

I see now that newer versions of Faststone as I have installed on my working computer no longer show those edge photosites. I had tested this with an older version that did show them. I'll have to use some of my development tools to look into those areas on your files.

Ill take a new lens cap shot and send it to you, as my current one is not straight from the camera, I compress my DNGs with Lightroom. Ill take this one after using live view for some time. Ill try mailing it to you, i know the file size is under Gmail size restrictions anyway...

Edit: I just tried taking the picture after 3 minutes or so of live view, and it looks quite different, its pretty much all magenta now, with the strongest noise present in the middle of the frame. The hard edge to the left is still present, but now the left part is darker than the brighter right part. Ill send this picture to you, together with another picture Ill take later when the sensor has cooled down.

I received the cold (31 degree Celcius) file by email but not the hot one. However, with the cold image I can try to see if hot/stuck pixels in the masked black borders are causing the left hard edge problem and will report back tomorrow.

The colour of the edge tinge will vary depending on the balance between the colour channels which could change with varying sensor conditions - not to worry as the correction algorithm auto-adjusts for different balances.

Regards, GordonBGood

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