Sigma fp: What's the Point of 12bit DNG RAW? One is True HDR Video

Started 3 months ago | Discussions thread
xpatUSA
xpatUSA Forum Pro • Posts: 17,725
Re: Sigma fp: What's the Point of 12bit DNG RAW? One is True HDR Video

bizi clop wrote:

xpatUSA wrote:

Note to Members:

In spite of the OP's dire warnings about blue sky 8-bit color and consequent banding, here is an 8-bit sRGB blue gradient. (Rec. 709 blue primary):

Pure linear blue, running from about 4% HSV value up to 100% at top, 1080px from top to bottom. Anyone see dire horizontal banding? Apart from the OP, that is ...

Well, there is a good reason why Stellarium includes a dithering option, up to 10bits.

https://github.com/Stellarium/stellarium/issues/131
"Color banding artifacts make atmosphere ugly in low light #131"

Here I made an example from two otherwise identical screenshots, one half is dithered, the other is not. (To be viewed only at 100%.)

Here I stretched the contrast with Levels to make it more visible, and also put the picture of the relevant settings:

So I think 8 bits are not always enough.

Nice example of banding!

Quite right, it doesn't take much post-processing for banding to show up in the 8-bit world - but I do not recall any mention of such post-processing per se by the OP.

(BTW, it's Bayer dithering applied here, invented by the same Bryce Bayer responsible for the Bayer mosaic.)

When I made my gradient, I did switch off dithering in the GIMP and of course I set the image precision to 8-bit integer so as to preclude any obfuscation.

In ImageJ a vertical profile plot of my blue gradient does reveal banding of more than one pixel - as does the blue channel histogram. However that banding is invisible in the posted view on my monitor and would be even more so had I produced a perfect gradient - which belies the OP's claim quite handsomely.

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