Vignette banding problem

[Doc_Pit]

[Benjamin Root]

If you flatten the image, does the banding clear up? I can't really see any banding, although the image is rather small.

[Doc_Pit]

Gentlemen, thanks very much for your responses.

Benjamin,

I'm inserting two images which, hopefully, will show the banding more clearly.  The first image shows the original.  The banding is most visible along the bottom left and running up the side.  The second two are sections of the flattened image.  There remains just a bare hint of banding in the flattened images, perhaps most visible in the last image.  It's more visible on the monitor than it is in these captures.

Davescm, I'm puzzled by your instruction. My vignette mask causes the banding, and my vignette mask is going to turn any layer below it to transparent along the edges, including any white layer.  My guess is that I'm misunderstanding you.  I have inserted a shot of my layers. Where would I insert the white layer as per your suggestion?

[davescm · Accepted solution]

You are fine with the black background.

The known artefact shows up only when viewing a gradient mask against the transparency grid. It is not the transparency, or the mask, that is the problem it is viewing it against the chequered grid. That is what is showing as heavy banding in your first image. This is a known issue, but does not impact on the actual image - as you do not view that chequered grid in your final image.

The second and third , do not show that artefact and  are just the mild banding that you will see on an 8 bit display and a smooth gray gradient. A little noise will help with that.

Dave

[Benjamin Root]

Much better, thank you. The banding that I see in the flattened images does look normal for an 8-bit image. I have to ask..Are you editing your images in 8 or 16 bit? What monitor do you have? If you are editing in 16 bit, the main culprit of banding is likely the display itself. Excluding the banding bug Dave mentioned. In order to get rid of that, just insert a white fill layer (or any tone/color you want) below all other layers.

[Doc_Pit]

I'm editing in 16-bit.  My monitors are Dell Precision Workstation 7710 4K, Dell U2713H, and Wacom Cintiq 21UX.  If I understand your comments, and those of Dave, correctly, my monitors are "true color" or 8-bits/channel, which implies that under some conditions (like the gradient situation I have described)  they can not display the finer color transition of 16-bits/channel that Photoshop can implement in its file.  Do I have that right?

Your comments have been enormously helpful.  Thanks.

[Benjamin Root]

I originally was talking about the files you posted here, actually.. Files that go on the web are 8-bit.

As for the monitor, most consumer models are 8 bit, as Dave said. Your U2713H monitor, however, seems to have a 14 bit LUT. If you are seeing banding in a flattened 16 bit image, you may want to recalibrate your display. If it is incorrectly calibrated you may see some banding.

[davescm]

I can't see the impact in your small screenshot.

However I do notice , you are showing the effect of the mask against the transparency grid. If you put a plain white layer behind the image do you still see it? There is a known issue ("bug") that shows an artefact against the transparency grid but does not impact when shown against a real layer. I suspect you may be seeing that. It is easy to check - just put a temporary plain layer behind the image. If it is that - then do not worry - it does not affect the actual image.

Dave