Panasonic Lumix G 20mm F1.7 II (H-H020A) - Banding

Started Aug 6, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Panasonic Lumix G 20mm F1.7 II (H-H020A) - Banding

tsi wrote:

I forgot that blue and red are on different rows in the bayer pattern. For some unknown reason I thought that they are mixed on the same row.

Even if blue and red were mixed on the same row, you might still see color shifts with the banding. Suppose for example, that both red and blue are significantly weaker (in RAW) than green as would be the case in a white area illuminated by daylight. If there is a positive read error for a row (or set of rows) due to the interference, it (they) will come out more magenta than average (because the error effectively boosts red and blue more than green). And if the systematic read error is negative, the row or rows will come out more green than average for the same reason.

The only difficulty I have with this explanation is that the bands would appear colored in all white balanced scenes. The examples I post are usually converted to B/W so it can not be seen there. However, I have not seen color bands in white balanced scenes unless the width of the bands is very wide (image of the spring). An explanation for this may be the color noise reduction, which eliminates color difference in narrow patterns. I am almost convinced.

Note that all you may see are rather subtle color shifts, as if you had altered the WB very slightly. Chroma NR probably helps partly conceal the phenomenon too, more so for thin than for broad bands. If I recall correctly (it's a while since I played with this now), I could see the color shifts due to the banding more clearly if I looked at the images without any chroma NR applied, e.g., in RawDigger (where I first looked at them that way) or in LR with chroma NR reduced to zero.

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