Color banding appearing on screen of gray image?

[jb7]

I see horizontal banding, but not in colour. Here, it looks like too much jpeg compression is emphasizing it...

[Brian K]

I'm using a MacPro 5.1, 8 cores, 32 gig RAM, ATI Radeon 5770 with 1 gig VRAM. The main monitor is an Eizo 21" ColorEdge CG 211. I have the graphics card also feeding my 27" iMac as a second monitor. OS is Snow leopard 10.6.7 (10.6.8 does not support proper calibration of the iMac when used as a second monitor). I have to use Snow Leopard because my scanner software, oxygen for the IQSmart, does not work with Lion.

The banding appears in the file at all sizes from 4400 ppi down to 950 pixels wide. 8 or 16 bit, rgb, grayscale, cmyk, Lab, does not matter. Tiff, PSD, PSB, or jpeg, does not matter. I'm wondering if the video card simply does not have the ability to support both monitors, but the problem still appears when just the Eizo is used.

[patrickjames]

What hardware/software are you using to profile the monitors?

I would recommend you dump the video LUTs (there is a free program called ProfileMenu that will allow you to do this easily http://www.macupdate.com/app/mac/26191/profilemenu ) then recalibrate and rebuild the profiles.

[Brian K]

Patrick the Eizo uses it's own proprietary calibration, and if I understand correctly it has it's own video card built in. As for the imac it's calibrated with a Gretag macbeth i1 photo UV cut.

[patrickjames]

I hate to help people out over the internet Brian, but I guess that is what we have. If you still have the problem I would recommend a couple of things. First, dump the dyld cache. You can do this through Terminal but I prefer to just clean the entire system at the same time with a program called Onyx which is free. I do this weekly. The dyld file clearing is under the Automate tab in Onyx. You will need to restart your computer afterwards. You should also do the video LUT clearing I mentioned above before the restart AND before you clear the dyld file. After restarting rebuild the calibration and profiles. I am assuming you are using Eye-One Match 3.6.3 with the Spectrophotometer. My guess is that these steps will fix your problem since the problem is spanning two monitors. Let me know if it doesn't and we can move forward from there.

[Brian K]

Well I tried the recommendations, and I appreciate all of those, and it hasn't seemed to really help. The problem is far more apparent on the iMac and much less so on the Eizo. I think what I will do next is buy a second video card and run each monitor individually on them.

[Peter Mounier]

I can see some banding. It is very subtle. If I move my cursor through the very ill defined edge of the red band the rgb values stay the same, but the cmyk values change by one percent in the yellow and magenta. When I move up to the green band. the rgb values remain the same but the cmyk values change in the opposite direction by 1%. I have very old Apple Studio display. It took me awhile to even see the what appears to be two bands, one red and one cyan, more or less going across the center of the image. Sorry, all I can do is verify that you're not imagining it.

Peter

[Peter Mounier]

I thought I'd try to find out if the banding that I see is a monitor or driver problem by creating a new document and filling it with gray. No banding there at all on my monitor with the test image.

Peter

[Lenny Eiger]

Thanks for the reply, the monitors are calibrated, they do use the same video card, but it's a new card..... did either of you see any weird color banding on the sample image?

No, but I did see some circular white scratches.

;-)

Lenny

[Greg Miller]

...but the cmyk values change in the opposite direction by 1%...
Peter

That's just how CMYK behaves. That happens with RGB files, but also with grayscale files. Create a canvas in Photoshop, set to grayscale, fill it with black, then put a gradient on it so the tones range from black to white. The use the color checker to sscan over the values and you will see the CMYK values are not all equal to each other. Do the same thing but in RGB mode and you will see the RGB values all equal each other but the CMYK values do not.