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Old 16th June 2019, 16:29   #1  |  Link
wonkey_monkey
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Dithered images look bad on my monitor - any idea why?

I've been experimenting with ordered dithering, but I've run into a weird thing where my laptop screen exhibits banding when I view a dithered gradient image at 100%.

Here's an image:



If I zoom in higher than 100%, even as little as 105%, the banding (which is like thin brighter or darker stripes) disappears.

I can still see the effect when I ramp up the levels of the dithered image:



The banding shifts if I nudge the image around my screen a pixel at the time.

Does anyone know what's causing this? I'm pretty sure I've disabled all colour corrections and stuff, and there's no sharpening or anything, but it's still visible. It's a Dell E6520 laptop with an UltraSharp FHD screen.
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Old 16th June 2019, 16:48   #2  |  Link
huhn
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win 10 1903?
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Old 16th June 2019, 16:55   #3  |  Link
wonkey_monkey
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Windows 7. What's Windows is putting on the screen is fine, so if anything is being changed it's being done by the graphics drivers (complicating matters, it's an Nvidia Optimus system so it has Intel and Nvidia working together). Or it's some intrinsic limitation in the screen itself.
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Old 16th June 2019, 17:32   #4  |  Link
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What software are you using to view the image?
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Old 16th June 2019, 17:40   #5  |  Link
wonkey_monkey
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It's the same in any software. Firefox, VirtualDub2, Photoshop...
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Old 16th June 2019, 23:19   #6  |  Link
Asmodian
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Is it pixel inversion or a similar issue?
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Old 17th June 2019, 00:42   #7  |  Link
poisondeathray
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Quote:
Originally Posted by wonkey_monkey View Post
it's an Nvidia Optimus system so it has Intel and Nvidia working together
To help determine if that is contributing -
In the device manager, you can disable one, repeat the tests. Then enable the other, disable the 1st, repeat the tests
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Old 17th June 2019, 17:32   #8  |  Link
wonkey_monkey
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I don't think you can ever really disable the Intel graphics, and the Nvidia only chips in when it's asked to.

In any case, after a bit of intensive research (Googling) I found out that apparently Intel on laptop screens is known for banding due to the way it dithers, and I found a nifty utility to allow you to control the dithering:

https://kawamoto.no-ip.org/henteko/myapp_en.html (search for "Dithering Settings for Intel Graphics")

Setting the dithering to "Spatio-Temporal 1 (better color)" (from the default of "Spatial (default)") almost completely fixes the problem, at the cost of some barely perceptible flickering.
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