fixing color banding/ posterization?

[Eric5]

I've recently begun digital painting in 16 bit mode RGB.  However, although my main monitors can't see it, I am ending up with horrible banding on either of my laptops or if posting online.  I convert to jpg with highest quality settings. 

This is a definite stumbling block to my work and I would appreciate suggestions as to how to eliminate asap.  I found a tutorial here, but it doesn't appear that AP has any such filter mentioned (spatter filter).  

Thank you! 

[Eric5]

I just wanted to update that making a flattened copy of the layers and placing it on top of the layers, and then doing "web safe dither" to the 16 bit document before exporting to jpg seems to have gotten rid of about 90% or more of the banding/ posterization.    I tried it both ways... just to the offending jpg itself and than back in the original 16 bit files.  If I do just the jpeg, it leaves it too noisy, but I don't see such noise in 16 bit.  

Hope this helps anyone else out too. 

[SrPx]

I wouldn't use JPG...

This is what I'd do: I'd work in 16 bits, keep a fully layered 16 bits file, in Adobe RGB or whatever your wide color space used. For exporting to other devices,  if you can't just directly flatten, I'd convert the file to 8 bits, and sRGB color space. The 16 bits come handy when working with gradients and very subtle effects (not always needed) , but you can convert afterwards, and I believe you need a dithering setting in the color conversion, but it should end up nice and showing no banding.  So, you export that "low end" version, even with layers, and the laptop might probably display it without banding. That's what I'd try. (as you should not see any banding, not even a 10%)

but don't use a JPG, or do so once all the file not only is converted as I mentioned, but also all flattened to one layer, and use very high JPG quality settings, if you really must use JPG for the web and can't afford a PNG or etc. (yeah, for the web, unless are small pics, it's gonna be typically a JPG...but it introduces several compression artifacts).

[duncang]

On 2/26/2019 at 2:37 PM, SrPx said:

I wouldn't use JPG...

This is what I'd do: I'd work in 16 bits, keep a fully layered 16 bits file, in Adobe RGB or whatever your wide color space used. For exporting to other devices,  if you can't just directly flatten, I'd convert the file to 8 bits, and sRGB color space. The 16 bits come handy when working with gradients and very subtle effects (not always needed) , but you can convert afterwards, and I believe you need a dithering setting in the color conversion, but it should end up nice and showing no banding.  So, you export that "low end" version, even with layers, and the laptop might probably display it without banding. That's what I'd try. (as you should not see any banding, not even a 10%)

but don't use a JPG, or do so once all the file not only is converted as I mentioned, but also all flattened to one layer, and use very high JPG quality settings, if you really must use JPG for the web and can't afford a PNG or etc. (yeah, for the web, unless are small pics, it's gonna be typically a JPG...but it introduces several compression artifacts).

Can you provide step by step instructions on how one does this.  I am running into a lot of posterization when downsampling photographs to jpg.  Thanks

[Fixx]

If you are serious about JPEG quality you could export to TIF or PNG and use a dedicated tool for JPEG compression. BN that many online services apply their own compression to uploaded art.