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Brush banding issue in 8 bit rgb - please cross check


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I am using a standard air brush in latest APh, Windows 10, sRGB color document.

In 8 bit mode I get banding - in 16 bit I don't.

I know that the internal blending of APh in 8 bit uses a non linear gamma curve (2.2 ?) which leads to blending issues. But I am not sure if this brush's beviour is also caused by this. Can somebody cross check?

brush banding.png

8bit.afphoto 16bit.afphoto

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In macOS I see the banding in your brush stroke but I don't get it with a new similar stroke. – You say "standard air brush" but your stroke does not show the typical spray spots of its texture but rather looks like a basic brush. What were your exact brush settings, respectively what do you get with a basic brush?

macOS 10.14.6 | MacBookPro Retina 15" | Eizo 27" | Affinity V1

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As mentioned before (and as expected) with an air brush / respectively with your brush settings I get a quite different brush result, both in editor preview and on canvas.

– What does your brush title "Selection" refer to?
– Did you edit the Texture, too?
– Why do you use a "Spray and Spatters" texture (!) brush to achieve such a soft brush appearance?
– Do you get banding with a "Basic" brush set to similar smooth look as your "Selection" brush?

240345034_brushbandingairbrushsetting1.thumb.jpg.d6764bdaf682027b7925184424a1073b.jpg

631182536_brushbandingairbrushsetting2.thumb.jpg.c42587d833036885d063b69dc8ab0490.jpg

macOS 10.14.6 | MacBookPro Retina 15" | Eizo 27" | Affinity V1

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1 hour ago, thomaso said:

– What does your brush title "Selection" refer to?

You get this if you open brush settings from the top toolbar. This alters the brush temporarily but leaves the base settings (right click -> edit on brush in brush list) unchanged.

 

1 hour ago, thomaso said:

– Did you edit the Texture, too?

No, default texture of this brush

1863037520_brushbanding4.png.12abcd0ee7a90179b002dbf09df88e6c.png

1 hour ago, thomaso said:

Why do you use a "Spray and Spatters" texture (!) brush to achieve such a soft brush appearance?

Because they work well for shading / masking of renders or render passes (the shown example is totally overdone, I only use a few strokes which gives very smooth and controllable effects).

 

1 hour ago, thomaso said:

Do you get banding with a "Basic" brush set to similar smooth look as your "Selection" brush?

Yes, but less obvious (example below - a few times forth and back in one stroke)

8 bit document

623397616_brushbanding5.png.de1263c2071ddc8cc27685d22a06318c.png

16 bit

1463141705_brushbanding6.png.4e909ca85b09bdd6c2fb20fe5affc925.png

Edit:

A 32 bit example. I know that APh uses linear blending when in 32 bit mode. Here it is perfect.

1384624398_brushbanding7.png.1b9d78ee62126b79d95ff3c1b3c17486.png

 

Anyway, 8 bit is good enough in most cases as well, but I had a few situations, where I noticed the banding. That's the reason I asked whether there might be something in the brushes to optimize.

And in general: "you, who you call yourself a 3D artist, are told to use 32 bit or you are doomed by the mighty goods of raytracing". I sometimes ignore this 🙂

Edited by cgidesign
32 bit example
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Okay, with a series of clicks (and reduced opacity) I can reproduce the banding with both an air/spray or a simple basic round brush for instance. Every click increases the banding that appears to increase with reduced opacity (= at the brush stroke edges).

2126590696_brushbandingmulticlicks.thumb.jpg.b9fc4fb0f92e4949ba1395659b42c741.jpg


This is obviously a known, logged and tagged (afp-1450) issue since years, for instance:

Interestingly an early moderator's response (2018) was that dithering is not supported for brushes, which feels contradictory with the "Dither gradients" option in the performance preferences and/or implies that opacity gradients are excluded (while I can't tell if this option has been implemented in the 2018 versions already) .

1466694060_brushbandingditheringpreference.jpg.9b56adba583dcb6a8eb200b41684b7f3.jpg

macOS 10.14.6 | MacBookPro Retina 15" | Eizo 27" | Affinity V1

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I made that report some time ago. The dithering we're talking about is brush specific, so it is not related gradients made by the Gradient Tool. You also probably wouldn't want dithering on every brush, so adding it as a toggle option in the brush editor would be a good idea.

At least you have found a solution that works. Nowadays I only work on 16-bit and 32-bit canvases because of this very issue. Luckily Affinity is significantly faster than Photoshop when working with higher colour ranges, so it is not a massive issue anymore. Still, I would very much like to have this fixed. :)

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17 hours ago, thomaso said:

Interestingly an early moderator's response (2018) was that dithering is not supported for brushes, which feels contradictory with the "Dither gradients" option in the performance preferences and/or implies that opacity gradients are excluded (while I can't tell if this option has been implemented in the 2018 versions already) .

 

A lot of topics in a single sentence 😉

regarding the “dither gradients” in performance settings:

  1. gradients are always dithered (when exported). You can only stop showing this while rendering within the App.
  2. you can suppress unwanted dithering only by tricks (add layer fx, color overlay, 0% opacity)
  3. i think this performance setting for gradients are totally unrelated to (pixel) brushes.
  4. If you paint with a brush on a pixel layer, there are 2 levels of anti-aliasing:
    1. anti-aliasing of the brush strokes itself, created during the strokes
    2. anti-aliasing on the layer (adjustable by cog wheel / blend range dialog, even after paointing)

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Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

My posts focus on technical aspects and leave out most of social grease like „maybe“, „in my opinion“, „I might be wrong“ etc. just add copy/paste all these softeners from this signature to make reading more comfortable for you. Otherwise I’m a fine person which respects you and everyone and wants to be respected.

 

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