Reader Comment, Sony A1: Horizontal Stripes in Blue Channel on Some Colors such as Sunflowers (PDAF banding?)
Reader Jan K writes:
I have to admit I rarely read your articles, but I am always impressed with your attention to detail when I do. I'm writing to you now because I think you might be interested in some quirky behavior of the sensor in the Sony A1.
Since I did not find any mention of this on the internet, I'm probably the first one to notice it (or just the first one to write such a thing about his 6.5k $ shiny new toy, haha). Let's cut to the chase, after this too long of an intro... the above is an animated GIF comparing JPEGs exported via CaptureOne and ON1 Photo Raw. I hope you can see clearly the black pixels in C1Pro export, as it's the only RAW processor I found that produces them (at least that explicitly). I thought that's a C1Pro issue, but after a long debate on FredMiranda's forum, I was able to confirm with others (through the use of RawDigger) that it's actually the RAW data coming from A1 (seen on 3 different copies) that contains significantly darker (in some cases black/nearly black) pixels in the Blue channel only. What's more, also stripes are visible in the Blue channel (RawDigger screenshot).
DIGLLOYD: I showed some lines like this back when I started my review, but they were not common.
Example — sunflowers
Sunflowers are so intensely yellow that they yield a blue channel that is very dark. So they can be an excellent subject for checking for sensor behavior.
Accordingly, this very morning, I took a few shots, and the results are seen below: under such conditions, obvious horizontal streaking (PDAF banding?) is visible in the blue channel in all color spaces (sRGB not shown because its dilettante-grade color gamut pins the blue channel to black).
I haven’t gone looking for other problems, but I am sure that what is seen here is explanatory for what reader Jan K writes. I would also expect that other intense color situations would show the problem, and perhaps in the red channel (such as with extreme-blue subjects).
PDAF pixels for focusing prowess are an anti-feature for photography quality. But we as buyers do not get any choice in the matter. No modern mainstream camera is free of them, the Panasonic S1R from 2019 being a rare exception (albeit not mainstream).