Banding evident in gradient layer

[Jetstream Rider]

I have cut out a subject from a photo and put it onto a gradient layer (light blue) - it looks good on screen. This I have done for 3 different images. They have been printed and on the prints there are magenta bands across the images.  I thought initially it was a printing problem, but when I looked back at the screen images, the banding is in the gradient layer, so it is an issue with the gradient itself.

How would I fix this?  Changing to a higher bit depth didn't seem to do anything - would I need to delete the layer and then add it again at a higher bit depth?  If I did that, how would I send it to the printer, as they only accept JPG and it would have to be downsized to 8 bit again? How do I get a non-banded gradient?  Thanks.

[D Fosse · Accepted solution]

Add a little bit of noise to the gradient layer. Not a lot, just enough to break up the banding.

Jpeg is the worst possible file format for this. Not only because it's 8 bit, but mostly because the jpeg compression algorithm compresses the color component much more aggressively than the luminance component. Color banding is very likely to happen with smooth gradients.

[Jetstream Rider]

Thank you - on screen that seems to have helped considerably. I'll have to try a print to see what happens.

I did build it all as a PSD to keep the quality good, but had to convert to JPG for the printer. It was the last step, but even so, its evident in the JPG but not the PSD.

[NB, colourmanagement]

I'd rotate 90 degrees and reprint to fully rule out printer issues.

Then try D Fosse's idea of adding a little noise to the gradient

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management

[c.pfaffenbichler]

Changing to a higher bit depth didn't seem to do anything - would I need to delete the layer and then add it again at a higher bit depth? 

If the Layer is a Gradient Layer then changing to 16bit should affect it anyway.

If it is a plain pixel Layer then it obviously would need to be regenerated or edited to take advantage of the additional bit depth. 

Did you check »Dither«? 

[Jetstream Rider]

Thanks.

Definitely not the printer, it's in the image. D Fosse's advice worked a treat. Thanks very much.