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General => Terragen Discussion => Topic started by: ackdoh on August 11, 2021, 12:41:30 pm

Title: Color Banding in Sky 32-bit Exr
Post by: ackdoh on August 11, 2021, 12:41:30 pm
Hey All,

I've been rendering blue skies (latest Terragen v 4.5.60) and noticing that no matter what I save it in, 16 bit half float, or 32-bit exr, at 16k spherical resolution, I'm getting subtle sky banding in the blue parts of the sky especially. Any idea how to get rid of that? Especially in post from some color correction, it gets more noticeable for sure. Attached are the 32-bit exr converted to 8-bit to save out as jpg's at maximum quality and the closeup.

Some forums searching about 9-10 years ago saying it could be the LCD monitor limitation but not sure as I haven't seen this banding on other sky photos I've taken or viewed in jpg.

David
Title: Re: Color Banding in Sky 32-bit Exr
Post by: WAS on August 11, 2021, 01:53:38 pm
Ill have to look on my PC as my phone is not showing any hard banding.

However, if your monitor isn't extended range you will just see banding and never what the 32bit image sees without it being printed out or changing to a better monitor.

My current monitor is 24bit simulated true color, so banding is harder to notice if the image is truly 16bit+
Title: Re: Color Banding in Sky 32-bit Exr
Post by: cyphyr on August 11, 2021, 03:25:22 pm
I'm looking on my (rather old Dell U3451W ultra wide monitor) and I'm not seeing any banding in your posted jpg's.

Downloading and cranking the levels in photoshop dose show a little in example2 but that could just be the jpg compression.

Sorry couldn't be more help.
Title: Re: Color Banding in Sky 32-bit Exr
Post by: pokoy on August 11, 2021, 03:33:42 pm
If your display is setup the usual way it's actually displaying colors in 8 bits (even if the image data is 16 or 32 bpc), so it is possible to get banding in gradients. A way to avoid it would be to use a graphics card and a display that use 10 bits for signal output and display.
Also, if you display images at anything else than 100% resizing can introduce banding depending on the method.

16/32 bpc means that internally, numbers are stored with a much higher precision, so you can tweak colors/levels in a much more extreme way than 8 bpc. But for the final display it's still within 0-255 range per channel which is why banding is still likely to occur in gradients.

I don't see much banding in the images you posted, either.
Title: Re: Color Banding in Sky 32-bit Exr
Post by: ackdoh on August 22, 2021, 01:10:43 pm
Thanks for looking at it all, I'll check my monitor settings as it seems that's the case here!
Title: Re: Color Banding in Sky 32-bit Exr
Post by: RogueNZ on August 22, 2021, 04:17:45 pm
It is sometimes a good idea to add some subtle noise in post work, I find this helps reduce the effect of banding, although I see none in your photos
Title: Re: Color Banding in Sky 32-bit Exr
Post by: WAS on August 22, 2021, 05:19:44 pm
Quote from: RogueNZ on August 22, 2021, 04:17:45 pmIt is sometimes a good idea to add some subtle noise in post work, I find this helps reduce the effect of banding, although I see none in your photos

This is true if it's already 16bit/32bit before being converted down to an 8bit jpeg or something. This allows the conversion to be much cleaner as the noise breaks up any smooth gradienting.

It doesn't quite work if it's a 8bit image, it'll just be noisy banding.