Hi,
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
name.
Any tips on how to ensure that the graphics card outputs colours verbatim
and undithered?
PC Spec
=======
Driver Packaging Version 8.97.100.3-120703a-142837C-ATI
Catalyst™ Version 12.6
Provider AMD.
2D Driver Version 6.14.10.7267
2D Driver File Path System/CurrentControlSet/Control/Video/{2D1F3F58-5AE9-46F3-B88A-9A1471B4A3B8}/0000
Direct3D Version 6.14.10.0911
OpenGL Version 6.14.10.11653
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 010.088.000.027
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
