Banding in uploaded photos in the gallery

[Snapper]

How do I avoid the 'banding' sometimes seen on uploaded photos in the Gallery (see my recent posting)? The original file looks ok in PS when scanned and resized, but when I upload the photo the sky has various bands of grey instead of a constant gradation.

The print was scanned at 300dpi, dust spots removed, then resized to 400x400 px, then 'save for web', and then uploaded to Apug gallery.

 

[Bob F.]

Looks fine to me on my 32-bit colour mode monitor. Switching it to the 16-bit colour monitor gives banding. Are you looking at it in 16-bit colour mode or lower?

Cheers, Bob.

 

[Snapper]

16-bit.

 

[Bob F.]

16-bit.

There you go then ...

Which does not explain why it looks OK in the graphics program but not when it's uploaded. Does it look OK if you drag the finished JPG file in to your browser? I suspect that it will not. I suspect that saving to JPG format adds extrapolated data to the 16-bit image file you are looking at, as part of the JPG algorithm, to convert it to the standard 24-bit JPG file. When this is then looked at on a 16-bit mode monitor, the banding is the result as it cannot display the extra colours.

But I leave the final answer to someone who knows more about JPG compression than I do!


Cheers, Bob.