This one had me stumped for quite a while. Whenever I used gradients in my layer mask for an image later, I would end up with really obvious banding, which really just ruined the photo in my case. Even with dithering enabled and using 16-bit color mode as all the identical online “solutions” suggested, I was still getting the banding at all zoom levels, even in the final render.
So what’s the problem? If you are using the 16-bit color mode and dithering already, most likely what you are dealing with is the result of lossy compression. Let me explain. When you are working on the project, you are going to see the banding no matter what. Why? Because Photoshop isn’t going to put the processing power into making a perfect gradient mask while you are working on your project, as this would severely effect performance. But the real issue comes when you render the final project. Presumably you are saving to a .jpg, right? That’s where the problem is being caused. When it renders the .jpg, it actually renders the gradient mask poorly to help make the file smaller.
So what can we do about it? Save the project in a lossless format first and then compress the resulting file to your liking. Here’s how:
1. File -> Save As
2. Select “TIFF” for the format. Check “As a Copy” to save it as one simple image file. Press save.
3. Load the resulting .tiff back into Photoshop.
4. Render however you normally render. You can make it a .jpg now if you wish, and the banding should be gone.
This drove me crazy for quite a while… I kept getting led to pages claiming that maybe my monitor wasn’t good enough, which was just wrong. Since I knew I wasn’t even dealing with a color issue (since it was a layer mask, not a color gradient), I knew there had to be some other solution. Eventually I figured it out! Let me know if this worked for you in the comments!