chemprof Offline Upload & Sell: Off
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genghis45 wrote:
rico wrote:
chemprof wrote:
This is 100% crop from the upper right corner (shade, window frame, smooth wall). Note that this is NOT an anomaly. Now that I know what I'm looking for, I can find it in ALL of my images, including out of focus areas in any image. It's most noticable in mid-tone areas.
Gerald
Hi, John! I'll let this thread play out until I get a full JPEG sample. Plus, I can borrow Gerald's crop for a quick assessment. From it, I detect a statistical imbalance between alternating pairs of pixel columns to the amount of almost 3%. This will be increaingly noticeable as the contrast curve is stretched. That column-pairs are involved implies that alternating Bayer cells (2x2 sensor sites in the RGGB pattern) are out of balance (correctable in firmware).
The algorithm I deploy in the following, rebalanced crop of Gerald's does appear to improve matters greatly:
Canon DSLR I have tested (D30, D60, 20D) also exhibit a systematic imbalance, although different in its pattern: the two G measures within a given Bayer 2x2 is inconsistent by about 1%. The effect is seen as a grid or mesh pattern, but often masked by JPEG compression. Noone is perfect, eh? 
Based on my quick results, I need to apply a secondary correction to fix some residual banding. Anyone with that full-sized D200 JPEG...?
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It appears to me that all that is being accomplished here, is that you're softening the image---which has a secondary effect of visually deemphasizing the banding artifact.
Scott
I agree that there's detail loss. That's one of the reasons I knew not to keep the D200 I had. I figured any processing would eliminate the apparently high level of detail in the images. Let's see what Rico comes up with with in the next pass, and let's continue to look for an answer from Nikon as well.
Gerald
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