FPN, or something else?

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Julian Dahl

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FPN, or something else?

PostMon Aug 07, 2017 11:05 pm

Skjermbilde 2017-08-08 00.35.00 copy.jpg
Skjermbilde 2017-08-08 00.35.00 copy.jpg (356.16 KiB) Viewed 874 times

Is this normal, or a bad sensor?
4.k Ursa Mini, slightly underexposed at 800 iso, Prores HQ at 4.6k
Mac Pro 7.1 48GB, RX5700 8GB, 12c, OSX 10.15.7
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Julian Dahl

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Re: FPN, or something else?

PostMon Aug 07, 2017 11:26 pm

Forget it, was only apparent in the Mac previewer...
Mac Pro 7.1 48GB, RX5700 8GB, 12c, OSX 10.15.7
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Dmytro Shijan

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Re: FPN, or something else?

PostTue Aug 08, 2017 3:09 am

This is Cross Hatching effect. Read about this problem here viewtopic.php?f=2&t=51936

Summary:
1. Wrong debayering of second green pixel produces semy-invisible fixed pixel grid which is partially hidden under the sensor noise. As a result at some zoom or scale levels in various players and apps this invisible grid may produce highly visible cross-hatch moire-like pattern.
2. Depending of image contrast, added sharpen and noise reduction amount, and player scaling method this pattern may be visible or not visible at all.
3. In BMMCC which is limited to 1920x1080 resolution this makes sensor Noise and FPN more visible (it behaves like some kind of shadow noise and FPN sharpening, adds additional digital artifacts to noise texture) and this limits the amount of visually usable shadow details.
4. People noticed this effect in BMPCC, BMMCC, BMPC and UM4.6K cameras. In BMPCC it is harder to see because it is slightly noisier than BMMCC and pixel pattern more hidden under the noise.
5. This effect depends of camera firmware version.
6. This problem can be fixed with fix in CornerFix app https://sites.google.com/site/cornerfix/using-cornerfix/maze-patterns-1 with applying a BayerGreenSplit500.cpf settings. This fix works only in ACR. All other RAW processing apps ignores it.
7. BM support team answer: "this is currently under investigation by our Development team"
8. BM team RMA few cameras but results are random and not perfect.
9. As a temporary solution for this problem shifting image position by setting X Y position to 0.5 works very well (note that in Resolve this works only with RAW footage, but in Adobe apps it works with both ProRes and RAW footage)
UPDATE: In Resolve, simply use the "pan/tilt" setting in the Color Tab (same values of 0.5 each), instead of "xy position" in the inspector. Should work for ProRes-Footage as well
BMMCC/BMMSC Rigs Collection https://bmmccrigs.tumblr.com
My custom made accessories for BMMCC/BMMSC https://lavky.com/radioproektor/

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