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View Full Version : Gradient Banding..... arghhhhhh!!!!



mrpapabeis
01-11-2008, 12:16 PM
I am getting consistent banding problems when using gradients. It started with a star background I made in VUE. Tried various settings and output formats, nada. So I tried an experiment. I made a gradient in Photoshop. Same banding problems. Added some blur to see if I could smooth it out. It made it worst. So I did some experiments in LW. First I applied the Sky_002.jpg as a texture, to a box object to see if the AA would fix it. Nope. Then I tried a LW gradient. Still banding (see second attachment). I am working at 1920 X 1080.

Somewhere this is a fundamental gap in my knowledge.


Thank you,

GP

cagey5
01-11-2008, 12:41 PM
Are you certain it isn't your video card settngs? You are running at 32 bit aren't you and not 16 bit?

mrpapabeis
01-11-2008, 12:55 PM
Yep, 32 bit PPC Mac, ATI Radeon 256 mb, OS 10.4.11, 4GB ram.

Cagey5- does the Star_02.jpg show banding on your system (full size)?



GP

Steamthrower
01-11-2008, 01:03 PM
Full size on this Core Duo Dell 1920x1200 laptop (at work they make me use PC, arghh...) and I show slight banding. It's not bad but it's there.

mrpapabeis
01-11-2008, 01:45 PM
Thanks inigio07,

I gotta fix this this. Slight banding becomes "funny laugh at" when projected.


GP

cagey5
01-11-2008, 02:36 PM
In all honesty I can't see it here.

kopperdrake
01-11-2008, 02:37 PM
I believe this is just the limitation of what is essentially 24bit colour trying to output two colours that are close to each other in value over a physically large spread. The maximum graduation between a light and dark value of a given hue is 256, so if your image is larger than that and what is essentially a very limited colour range you will likely notice some banding - here is a quote from people on a Max site with the same problem:

"As I mentioned earlier all 3dsmax renders are processed at 48bpp (16bit for each color channel) internally. But here is the kicker. There is no monitor or display today, capable of displaying 48bpp. Your gfx card and lcd monitor is only capable of showing 24bpp of color information. And with 24bpp you only have 256 possible gradients for each of the main color red, green and blue. So a perfect 24bpp single color gradient can only be 256 pixels wide. Anything wider will result in banding.

As many have discovered, inserting noise/dither in the gradient will mask the banding. But for some reason 3dsmax use a linear 48bpp->24bpp conversion algorithm without dither, when previewing and saving renders as 24bpp images.
Photoshop on the other hand, does a much better conversion.
48bpp->24bpp conversion

So there are two ways to reduce banding.
1. Save 3dsmax render as 48bpp images and do the 24bpp conversion in PS or alike.
2. Add a small amount of noise using the "Film Grain" effect in 3dsmax or the noise filter in AE."

Hope it helps...they get it worse with no dither pattern being applied to the 8 bit image before output! For animation I'm sometimes asked to produce files as 48bit images, 16bits per each of the RGB channels as opposed to the standard 8bits your monitor can display. After Effects will open them but still on screen they look like they're banding as the monitor just can't cope with the colour range it's being asked to display - I assume AE has to knock it down to a 24bit representation in order for the graphics card to display it.

We also get this in print too - our technique there is to add noise to the gradient which fools the printer into creating a scattered effect which is unnoticeable to the eye. A similar effect is used by AE to display it on the monitor.

mrpapabeis
01-11-2008, 04:29 PM
The attachment was done in AE. I used the "4 color gradient" effect. Copied the blue color to the other four colors, and changed the saturation on them. Same color. Voila! Banding.... I've tried adding noise, but it takes a visible amount of noise to smooth it out. So far... I'm going to try Shake next.


GP

mrpapabeis
01-11-2008, 04:45 PM
Shake too...

Greenlaw
01-11-2008, 05:46 PM
Are you rendering using the F9 command? If so, make sure you're using ImageViewer FP, and not the default ImageViewer which is more likely to show banding.

If your post editing/composting programs supports .exr, I suggest using this format to avoid banding.

Hope this helps.

DRG

Surrealist.
01-11-2008, 06:16 PM
The attachment was done in AE. I used the "4 color gradient" effect. Copied the blue color to the other four colors, and changed the saturation on them. Same color. Voila! Banding.... I've tried adding noise, but it takes a visible amount of noise to smooth it out. So far... I'm going to try Shake next.


Perfect gradient. No banding here.

If you are having this problem in many programs you might try to look at it on another PC and consider that this may be an issue with the machine you are using.

Maxx
01-11-2008, 06:39 PM
I'm with Surrealist - I'm not seeing any banding here. Perhaps it's the graphics adapter?

mrpapabeis
01-11-2008, 07:25 PM
thank you to all who have chimed in at this point.

1) .exr seems to help some. But there is still some banding.

2) Cagey5, surrealist, maxx... I really don't want to sound like an idiot.... but are you viewing the images at full size? The 1st star image is a 2k image (1920 X 1080). The banding shows up at full size. If you are viewing at full size let me know. Please?

3) There is a possibility that I have a graphics card problem. I'm going to check for new drivers. My monitor is a 24" lcd a doublesight DS-240WB. Its at max resolution of 1920 X 1200. I think I'm running into what kopperdrake
referred to in his post.

4) Mr. Greenlaw, you guys work with 2k and 4k plates all the time. Have you ever had any problems with banding?

5) There are HDR 16 bit monitors out there but they are very expensive.


GP

Jarno
01-11-2008, 07:36 PM
Looks perfectly fine for me too. Maybe there is some sort of gamma correction turned on for display? That could squash some values which are originally only slightly different into the same value.

---JvdL---

Surrealist.
01-11-2008, 08:59 PM
2) Cagey5, surrealist, maxx... I really don't want to sound like an idiot.... but are you viewing the images at full size? The 1st star image is a 2k image (1920 X 1080). The banding shows up at full size. If you are viewing at full size let me know. Please?
GP

OK, sorry my bad. I thought I had tried to zoom it in but I guess not.

At full size I do see a slight amount of banding in the star image (only at the bottom) and the gradient you posted further down (but not in the one next to the star image)

Though I am not 100% it is what you are seeing. What I am seeing is so subtle it could be the jpeg compression.

Would you describe it as subtle and relatively thin bands?

That is what I see.

mrpapabeis
01-11-2008, 09:02 PM
I switched to PC gamma. Less banding. I'll stay at this setting for a bit.


GP

mrpapabeis
01-11-2008, 09:10 PM
OK, sorry my bad. I thought I had tried to zoom it in but I guess not.

At full size I do see a slight amount of banding in the star image (only at the bottom) and the gradient you posted further down (but not in the one next to the star image)

Though I am not 100% it is what you are seeing. What I am seeing is so subtle it could be the jpeg compression.

Would you describe it as subtle and relatively thin bands?

That is what I see.

Yes, subtle bands when viewed in PC gamma. In Mac gamma (1.8) they scream. Also the clouds look like a topographical elevation map.

My concerns are twofold. The project is being edited on final cut pro, mac gamma probably. And when projected on a big screen, how noticeable will those bands become? Time to scare up a 2k projector.

Surrealist.
01-11-2008, 10:12 PM
Yes I would. Definitely do some testing on the output medium. Good luck with it.

Red_Oddity
01-15-2008, 02:39 AM
What sort of monitor are you using.

Remember, a lot of LCD monitors display only 6bit in every channel to keep manufacturing cost of the display low.

BUT, when you use a primary color (in this case blue) you only can have a single different color on a line in a range of 256 pixels (even when working in float, as you video card is onlyy capable of displaying 8 bits per channel, unless you work with a HDR monitor and a card that support said HDR output)
So when your image is going to be higher than 256 pixels, you are going to notice banding (without dithering or noise).

dwburman
01-15-2008, 11:57 AM
FCP won't necessarily work with the Mac gamma. It's a video app so it can be set to use video gamma and color space. (I believe PC gamma is closer to video gamma than the Mac gamma is) If you want to reduce banding in FCP you can use a 10-bit codec.

There's a chance the video projector itself will have to be tweaked and that's not always an easy thing to do.

If the project is going to be compressed, the brightness/gamma might change during that process.

Every screen you view this thing on probably will be slightly different unless they've all been calibrated into consistency.