Photoshop CC: Contrast and Gradient tool problem with lines across image (banding/quantization)

  • 1
  • Problem
  • Updated 5 years ago
  • Solved
  • (Edited)
I purchased Photoshop CC a few months ago and it was working well, but over the past 2 or so months when I use the gradient tool or the contrast tool it creates slight lines across my image. I have asked many photography and laptop experts but they can't seam to find what the problem is. Please can you help me with this issue?
Thank you, Kind Regards, Robin Clark
Photo of Robin Clark

Robin Clark

  • 4 Posts
  • 0 Reply Likes
  • frustrated

Posted 5 years ago

  • 1
Photo of Chris Cox

Chris Cox

  • 20280 Posts
  • 813 Reply Likes
What straight lines are you referring to?

Have you installed all the Photoshop updates (should be on 14.1.2)?
And what OS version are you using?
Photo of Robin Clark

Robin Clark

  • 4 Posts
  • 0 Reply Likes
Hi Chris
Thanks for your reply. They aren't straight lines but they are slight/feint lines that curve around the area where the gradient or contrast tool is applied.
I do have version 14.1.2 x64 on photoshop
As for OS I am using OS X version 10. 8. 5.
Thanks again,
Robin Clark
Photo of Chris Cox

Chris Cox

  • 20280 Posts
  • 813 Reply Likes
OK, so you're seeing banding (aka quantization). Banding is a result of the limited number of levels available for intensity in your document or your display. Banding can be made more visible by extreme adjustments, bad display profiles, and some bad displays (especially cheaper or older LCD displays).

By increasing the contrast, you make take values that differed by a small amount, and make them differ by a larger amount - increasing the possibility to see the difference in values.

The usual solution to banding/quantization is to add a very small amount of noise (like 0.5 % or less).
Photo of Robin Clark

Robin Clark

  • 4 Posts
  • 0 Reply Likes
Thank you so much for your help! Adding 0.5% of noise has really helped!
I bought a new apple mac book pro a few months ago with a retina display so it can't be the display causing the problem.
Doesn't the image quality decrease when you add noise because you are essentially adding grain? A slight bit of gain is of course better then banding but are there any other solutions? It just confuses me why for the first few months I didn't experience this problem with my new laptop and Photoshop. It makes me wonder if I pressed something that's making it happen and I haven't realised it. Is this possible?
Thanks again!
Robin Clark
Photo of Chris Cox

Chris Cox

  • 20280 Posts
  • 813 Reply Likes
The quality decreases slightly, but the added noise breaks up the edges.
So you want to add the noise as the last step, after making all your adjustments and cleanup.

Using a 16 bit/channel source helps - but your display is still 8 bit/channel, so you may still see banding when the image itself isn't too bad.

Banding can be made more visible on some displays, or due to extreme adjustments (making a small difference into a large, visible difference in values).
Photo of Robin Clark

Robin Clark

  • 4 Posts
  • 0 Reply Likes
Thank you so much for all your help and explanations. This is really useful advice and I am very relieved to have resolved this problem. Your time is much appreciated.
Best wishes,
Robin Clark
Photo of Chris Cox

Chris Cox

  • 20280 Posts
  • 813 Reply Likes
You're welcome.