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Journeyman III

Disabling Unwanted Dither


I'm new here, so apologies if this is not the best forum to be posting on.

I work for a company which makes digital displays, and I'm currently doing

some work on the accuracy of colour rendering.

Our display accepts DVI and DisplayPort, and while it can both dither and

gamma-correct images, I currently have both features turned off, so that

what appears on the display should exactly match what comes in from the

graphics card. Our display is natively RGB at 8 bits per colour.

I have a test image containing a green square, with a uniform pixel value

of (0, 127, 0). When I feed it to our display, I get a dithered image in which

some pixels are at level 127 and some at 128. As mentioned above, our own

dither/gamma unit is turned off, but to completely eliminate any malfunction

in that, we have sampled the video as it comes in to the system (before it

even enters our gamma/dither unit) and the dither is definitely present.

On moving our display around from one PC to another, we have found that

even with identical graphics cards, the unwanted dither does not always

appear - we found it on two of our three HD 3600 PCs. On the third PC, there

was no dither, and the image was exactly as it should be. The common spec

of all three PCs is below.

The unwanted dither has been reproduced on both DVI and DisplayPort outputs.

I couldn't see any dither control in Catalyst, but maybe it goes by another


Any tips on how to ensure that the graphics card outputs colours verbatim

and undithered?

PC Spec


Driver Packaging Version  

Catalyst™ Version         12.6

Provider AMD.   

2D Driver Version 

2D Driver File Path         System/CurrentControlSet/Control/Video/{2D1F3F58-5AE9-46F3-B88A-9A1471B4A3B8}/0000

Direct3D Version  

OpenGL Version  

Catalyst™ Control Center Version           2012.0703.2356.41139

Primary Adapter

Graphics Card Manufacturer        Powered by AMD

Graphics Chipset           ATI Radeon HD 3600 Series

Device ID           9598

Vendor  1002

Subsystem ID    2242

Subsystem Vendor ID    1028

Graphics Bus Capability PCI Express 2.0

Maximum Bus Setting    PCI Express 2.0 x16

BIOS Version

BIOS Part Number         113-B38201-104

BIOS Date         2008/08/05

Memory Size     256 MB

Memory Type    DDR2

Core Clock in MHz         725 MHz

Memory Clock in MHz    500 MHz

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