PDA

View Full Version : Linear Gradient showing lines through it (banding?)


WiLSoN-adrift
09-10-2009, 03:27 AM
Can someone help me?

EVERY TIME i make a linear gradient (possibly even any other sytle gradient but have not tried), be it on whole canvas or adding gradient in blending options layer style (to type text), i get this ugly bunch of lines going through it. (i have been told this is called "banding" is that right?)

I have tried saving image as png, jpg and even bmp, but still showing lines. Is there any way or method to avoid this? Surely gradients are not destined to have horrid lines through them.

Example pic link below of my problems.

Please Zoom in on pic to full size to ensure seeing my problem.

My problem --> http://img196.imageshack.us/img196/5408/testgradient2.jpg

Any help or advice would be greatly appreciated.

Thanks,
WiLSoN

SilverCity
09-10-2009, 03:50 AM
If you're going to save to a lossy file, save at the highest quality setting. Have you tried a tiff or psd file? The more compression you have, the more banding. Also, the type of monitor you have will change the appearance of gradients. If you want to save to a jpg or lossy file, add a little noise to the gradient to lessen the banding.

WiLSoN-adrift
09-10-2009, 05:45 AM
Well i tried saving as jpg (highest possible, 12) also saved as png and bmp. Banding appeared on all of them. Have not tried a tiff file, not really familiar with tiff. As far as psd, i am actually working within a psd. but i want to be able to finish a pic that can be posted and viewed via webpage. That being said, i can even notice the banding on my psd. Now the thing is i have sent the pic to a number of friends and they all see the banding on their machine as well. My monitor is pretty sweet so i tend to not think it's my monitor.

I haven't worked alot with gradients and just don't understand them fully i reckon, because it actually spins me out about the banding. Had it in my mind that photoshop is just such a badass program (and it is) that it would easily and automatically make a smooth gradient no matter what, lol, i am an idiot.

Thanks heaps for the info and the willingness to help, will give a go to the "noise" thing. Will that in any way hurt the appearance of the gradient?

SilverCity
09-10-2009, 06:12 AM
Do you have Dither checked in your Gradient Tool settings?

Here is one way of adding noise:

http://www.garryblack.com/ad04.htm

You can also add noise to individual channels (the channel with the more banding gets more noise added).

gruhn
09-11-2009, 12:32 AM
The limitations of 24 bit color RGB graphics are not due to Photoshop being kickass or not.

Your example is in cool colours. Humans can discern more greens than they can the warmer colours and, iirc, 24 bit RGB takes a hit there.

Zoom in close. Find a band. Use the eyedropper. Click different places inside the band. Do the colour values change? If yes, then PShop is doing better than you are seeing. If no, then it is a band. Click one band then the next one over. Does only one colour value change by only an amount of one? If yes, then PShop is doing the best it can. If no, then I'm surprised.

Another thing that happens with more subtle colours is that as one channel moves and the other ones don't there is hue wobble [new term!] from band to band. That makes them extra easy to spot. (and frustrating and kind gross too).

You mention all the ways you saved it. If the banding appears in PShop when you are drawing then it doesn't matter how you save it.

One assumption JPEG makes is that value is more important than color (convert an image to lab; abuse the A and B channels. Blur them, pixelate them. You will see that this assumption is true.) So when you save the subtle gradient to a JPEG the algorithm says "wow, these colours are pretty close. I'm gonna toss 3/4 [made up number] of them." My impression is that it is even more abusive with the more muted colours than it is with the clowns.

In the end, you will have to wait until everybody has more dynamic range and Photoshop defaults to a useful bit depth.

Oh yeah, on the eyedropper test, you should (though for some reason I'm not. sometimes.) getting different values as you click in a band if you had dither on.

I haven't fancied the results from adding noise with "add noise". I like "glass distortion" better but it's weaker. But that's why I like it.

CGTalk Moderation
09-11-2009, 12:32 AM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.