Anti-glare sparkle
Overview
Anti-glare sparkle is a side-effect of the anti-glare treatment applied to your pen display. How much AG sparkle is visible depends on a lot of factors. Generally, people want very low amounts of AG sparkle.
Companion video
Because this is a visible phenomenon, watching the video I made on this topic may be a good starting point. https://youtu.be/g_nsvraK3P8
Overview
To prevent reflections and room lighting from interfering with your drawing experience, manufacturers of pen displays provide an anti-glare treatment.
The treatment comes in two forms:
anti-glare etched glass
anti-glare film
The physics of the anti-glare treatment produces an effect called anti-glare sparkle (AG sparkle).
AG sparkle is hard to describe in words, but overall it will look like a grainy look.
What it looks like
Photographing it or filming it is very tricky.
Depending on the camera settings...
the effect can disappear
the sparkle can look very different from what your eyes see.
you might notice it more with some colors than others
Example 1
The the pictures below show screens that are showing black, white, and gray pixels.
The one on the right represents an mor extreme example . You can clearly see that different "color grains"

Example 2
It could also look like this - this is a very close up view

Example 3
I found this in a reddit post. The AG sparkle is everywhere but is most noticeable in the green area.
How manufacturers refer to the AG treatment
Huion Kamvas Pro 24 (4K) [GT2401]
XP-Pen Artist Pro 16TP [MD160U]
Wacom One [DTC133]
Buying a tablet
You MUST research AG sparkly for any tablet you are intend to buy.
I see many people buy tablets and not realize the AG sparkle might be present. And so they get very frustrated with their purchase.
DO NOT rely on photos provided by the manufacturer. These photos never show AG sparkle. It's probably not even deliberate that AG sparkle isn't shown because it is very tricky to photograph.
You need to ask people who use the tablet if the tablet exhibits the effect and how much the effect is visible.
Prevalence
AG sparkle is varies depending on the model of pen display.
All pen displays that I know of will have some amount of it because they all have some kind of anti-glare treatment.
Contributing factors
Your perception of AG sparkly will be affected by several factors.
The nature of anti-glare treatment. Some tablets models in general seem to use a very intense AG treatment and others have a much milder treatment.
The distance between your eyes and the tablet. What might be strongly noticeable at 1 few inches might be essentially invisible at a normal drawing distance.
The pixels-per-inch (PPI) of the display.
High Pitch (PPI) displays
High-pitch means lots of pixels per inch (PPI).
For example:
4K on a 27" pen display has a pitch of 163.7 PPI
4K on 16" pen display gives a pitch of 281.4 PPI
AG Sparkle will appear more on high-pitch displays
If the same exact AG treatment is used on those two displays you will notice it more on the 16" display.
Reddit threads
r/huion - https://www.reddit.com/r/huion/comments/13ikmph/ - This deleted reddit post has an video thet perfectly demonstrates the shimmering effect of the sparkle.
r/huion - Is this normal? Possible display issue? noisy output? 11/23/2022
References
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