As my first post in this forum let me contribute something to the VP930 Dithering issue.
First of all I can definitively confirm that the VP930 has an issue with certain color bands flickering with strange pattern that remind of dithering patterns, but most likely this is a
defect of the electronics! I had two monitors exchanged by Viewsonic already, now I am using my third try. The Viewsonic hotline statet that this is a
known issue and they offered several other people to exchange the monitor with a VP201. I did not want a 201 and they told me that they cannot asure me that a new monitor would solve the problem. Obviously it did not solve anything because I had to send it in again. The second one was far worse than the first one, the third one is quite ok, but you can still find the flickering in some colors. The first monitors lacked a good heap of dark green colors (where all just black) resulting in very obvious color banding, the third shows the full range of 256 shades of green. So all of those three tries behaved somehow different, which underlines my suspicion that the electronics are bugged.
Concerning the discussion if the VP930 uses 6 Bit + 2 Bit dithering as stated by the german site (which also states it's 16.7 mio. colors!?), 8 Bit like the VP191 did as statet by the british site (which also states it uses 16.7 mio. colors) or 8 Bit + Dithering. I would say that it uses 8 Bit + Dithering, just like the Eizos do!
With my VP191 it was very easy to find the only one setting that allowed me to use the full range of 16.7 mio. colors. Like with all 8 Bit displays you had to throw away a no. of colours if you changed contrast or color-temperature (RGB channels). With the VP930 I found that once you increase contrast over 70% with RGB all at 100% it shifts white down to the lightest shades of grey effectively replacing them with white while darker shades of grey become lighter.
So why am I quite sure that it's not 6 bit + 2 FRC dithering? Because I have seen a VP171 which uses an 6 bit + 2 FRC TN-panel. Dithering works very good on this monitor but it's still discernable. Also I made myself some pictures to test all gradients of grey, red, green and blue, each picture showing all 256 shades of the coresponding color. A 6+2 bit display could only display 64 pure shades while dithering 253 of the other shades and leaving 2 shades out completely. At least for my eyes the VP930 displays all 256 shades very well (despite the very few that show the mostly red flickering issue). Plus it does so when you lower contrast or color settings, which speaks for at least 8 bit. If those patterns mentioned earlier were pure dithering then you would see them on
most shades, not only a handfull of them. But when you decrease contrast or even any color-channel (RGB) no colors are thrown away at all, they all just become darker. For an 8 bit panel this must mean that some kind of dithering is used either or brightness is reduced. The second is not the case because you can see that those few flickering shades are shifted further up the scale as you lower contrast.
Acutally that is quite a feature which Eizo uses to brag about ("10 bit look up table, 1.07 billion colors bla"). But unfortunately it seems as if Viewsonic has not managed to get the control-electronics right. I suspect that those
very obvious flickerings are due to improper dithering while we don't even see the dithering that is properly used on all the other colors.There is another flaw in the color settings that supports that there is something wrong with the electronics. When you manually set colors and change one of the basic color (red, green, blue) by just one percent the whole color-channel is increased by +11%, even if you actually decreased the channel! That means if you set all three channels one down and one up again you effectively increase the contrast by +11%. If after that you change the contrast by just 1% the colors turn back to normal. So if you want to manually set colors you first have to decrease contrast by -11%, then set all three channels at least one up and down, then you can set colors to your liking and after that you increase contrast by +11% again.
If you want to see the strange (mostly red) flickering on your VP930 for yourself then do the following (via DVI, analog may show different colors). You will most likely see a dark grey screen with alot of moving red dots and lines on it. If that doesn't work play a bit with contrast and different color settings.
- switch to sRGB colors via the monitor
- turn brightness to 113% via your
graphic-card driver
- show a black screen
These are the gradient charts I made myself and used for testing. Each shows all 256 shades of the given color, 16 shades per line, 16 lines total. Above each line you see two bars, the left bar uses the same color as the outer left shade of a line, the right bar shows the same color as the outer right shade of a line (that helps to discern the shades from each other). Use the charts in fullscreen at 1280x1024 for best results, there is a black border around them to compensate for backlight leacking at the corners of your typical Viewsonic/AU Optics panel.
contrast_grey.png
contrast_red.png
contrast_green.png
contrast_blue.png