Can anyone please explain the reason behind this "Noise Banding" on transparency?

[puraidodes]

I understand gradient banding. There are fixes.

For these, usually, I'd just paint over these kinds of issues in images or clone them and smudge them. I can't quite remember if I've seen this in an older Photoshop version – maybe I forgot.

When I'm working with transparency and I paint, this tends to happen. I'm just using the default soft brush without tweaking any settings. That hard noisy splotch and then surrounded by softness.
But it looks fine when there is color underneath.
Strangely, I've noticed this same thing occurring in some images, even when there's a background.

Why does this happen? Is there some logic behind it?
If anyone could shed some light on this, I'd appreciate it. Thanks!

 

[thebestcpu]

I understand gradient banding. There are fixes.

For these, usually, I'd just paint over these kinds of issues in images or clone them and smudge them. I can't quite remember if I've seen this in an older Photoshop version – maybe I forgot.

When I'm working with transparency and I paint, this tends to happen. I'm just using the default soft brush without tweaking any settings. That hard noisy splotch and then surrounded by softness.
But it looks fine when there is color underneath.
Strangely, I've noticed this same thing occurring in some images, even when there's a background.

Why does this happen? Is there some logic behind it?
If anyone could shed some light on this, I'd appreciate it. Thanks!

View attachment 139170

HI @puraidodes

That is a very interesting observation. From my past understanding and some present investigation, here are a couple thoughts (my understanding not proven experiement yet)
- It is important to know that the softness around a brush is created from the transparency channel and not the color mode (will still be 8 bit even if in 16 bit mode)
- Transparency channels as I understand are always in 8 bit mode not matter the settings you use.
- So I believe the arithmetic computations done may have different "bitness" if transparency is involved
- I also noted that if I set the color mode to 16 bits the transition is smoother (go figure). So give that a try.

So I have not gotten to root cause nor understand Adobe's logic here. I also have not tried all the other modes such as smoothing and flow to see what difference is any those may impact.

I will close with a couple images to make it clear when showing that the edges are controlled by the transparency channel:

Here is a single brush mark on a transparent background:



Here is the same image put pulling out the transparency to a Layer Mask via Layer > Layer Mask > From Transparency (note the thumbnails in the Layer Panel shown:



Here is the same image yet disabling the Layer Mask. Note that a single brush drop is just a color square with transparency:



And when viewing the Layer Mask by itself, you can see that the roundness and edge are controlled totally by the transparency:



Again I have not taken it further other than to provide what I observed on short order.
Hope that helps some
John Wheeler

 

[puraidodes]

Here is the same image put pulling out the transparency to a Layer Mask via Layer > Layer Mask > From Transparency (note the thumbnails in the Layer Panel shown:

Here is the same image yet disabling the Layer Mask. Note that a single brush drop is just a color square with transparency:

Oh, Have been using Photoshop for some years and never noticed this. That's interesting!

Thank you for the explanation.

What version of Photoshop is this, if I might ask?

Recently had to re-install my OS. I thought I would try and use my old CS6 version. My brush incident was in CS6.
Previously had the CS5.5 version I never had problems, I think. Maybe I'll go back to it. Newer ones are good but some things are best in the older versions.

 

[thebestcpu]

Oh, Have been using Photoshop for some years and never noticed this. That's interesting!

Thank you for the explanation.

What version of Photoshop is this, if I might ask?

Recently had to re-install my OS. I thought I would try and use my old CS6 version. My brush incident was in CS6.
Previously had the CS5.5 version I never had problems, I think. Maybe I'll go back to it. Newer ones are good but some things are best in the older versions.

You're welcome @puraidodes

My present version is PS 2023 release 24.5 yet I don't think any recent version is the same. No longer have an OS that will run that far back so cannot confirm if it is different. If you see that you get a different result, please let us know.