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04-07-2009, 07:09 PM   #46
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New info and ideas.

QuoteOriginally posted by Henkezd Quote
Hi, I got an K20D as an replacement for my K10D that pentax took back, the problem is that this new K20D I got works even worse than my old K10D

More about the other problems later, first of all, it makes images blue in the lower border on higher iso, depending on object it shows more or less.
To show this I made an video with some samples that I put up on youtube.

YouTube - Pentax K20D Noise

Best Regards Henrik
In regards to the color banding it seems that one reason for this is a problem w/ the black point setting. Here is an example from a Canon 5d MkII. Now I'm not picking on Canon per se but you need to read the concurrent thread to get some ideas of the causes of this.
Purple periphery of 5Dmk2 images: Canon EOS-1D / 1Ds / 5D Forum: Digital Photography Review
Re: Purple periphery of 5Dmk2 images: Canon EOS-1D / 1Ds / 5D Forum: Digital Photography Review

If it is far worse with under-exposure, and/or high ISOs, there is a blackpoint problem with your sensor, and it needs to be swapped out.

Take a (preferably RAW) shot at ISO 25600 with the lens cap on, and crank it up in conversion, or PP. If the problem is there, coloring the noise unevenly, then it is the sensor.

A bit of conversation and speculation from the same thread:
> Edit: I just tried making the same test with my old 20D. The frame
> looks similar, but is much more homogenous with 20D -- no brighter or
> darker areas like there are in 5D image. The darker areas in 5D image
> correspond well with the magenta-shifter areas in the in the first
> post. Now if other 5DmkII owners could perform this test to see if
> it's feature of the sensor or not.


I've heard that CMOS sensors don't start with no charge and build it up with photon hits; they start charged to a certain level and the photons knock this charge down, so that what we really have is a negative of sorts. Perhaps what is happening is that these photosites are not charging evenly, the way they should, if this is true.


Last edited by jeffkrol; 04-07-2009 at 07:16 PM.
04-07-2009, 10:38 PM   #47
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QuoteQuote:
jeffkrol: In regards to the color banding it seems that one reason for this is a problem w/ the black point setting. Here is an example from a Canon 5d MkII. Now I'm not picking on Canon per se but you need to read the concurrent thread to get some ideas of the causes of this.
Purple periphery of 5Dmk2 images: Canon EOS-1D / 1Ds / 5D Forum: Digital Photography Review
Re: Purple periphery of 5Dmk2 images: Canon EOS-1D / 1Ds / 5D Forum: Digital Photography Review
Thanks Jeff--an excellent contributiuon to this thread.
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