bobdobbs wrote:

Hey guys.

I created an A4 sized canvas and made a black background layer.

On a new layer I wanted to create a large lighting effect that would use most of the area of the canvas:

new transparent layer -> select fg to transparent radial gradient...

But I got banding.

I selected dithering, and still got banding. I used a large, circular self-created circular fuzzy "lighting brush", and tried to create the same target effect. Still got banding.

What's the solution to this?

Is your image in indexed or RGB mode? Is your gradient monochrome? What is its size?

Say you draw a monochrome gradient from back to white along 2560 pixels. You only have 256 different colors, thus you get bands 10 pixels wide. And dithering does not have a real effect in such a case.

7/28/2010 9:14 AM keltezéssel, bob írta:

Say you draw a monochrome gradient from back to white along 2560 pixels. You only have 256 different colors, thus you get bands 10 pixels wide. And dithering does not have a real effect in such a case.

I'm in RGB mode. The image is 2480px wide and 2794px high.

Is there a way that I can create a smooth gradient? Will switching to another colour mode help?

How can I work this out for myself in the future?

Hi,
I experience that a slight HSV or RGB noise can get rid of the bands. In case of RGB noise, I see nice results with settings: Correlated noise and Independent RGB switched off, and all channels set to 0.04.

However, of course, this adds a noise to your picture, so it can not strictly be called smooth, but at least you don't have bands.

Abel

bob wrote:

Say you draw a monochrome gradient from black to white along 2560 pixels. You only have 256 different colors, thus you get bands 10 pixels wide. And dithering does not have a real effect in such a case.

I'm in RGB mode. The image is 2480px wide and 2794px high.

I tried the same size with a gradient from black to white, and another from red to green. In my opinion, the banding effect is not really obvious, but maybe my sight is not as sharp as yours. Anyway, it is still less obvious in the polychrome gradient.

Is there a way that I can create a smooth gradient? Will switching to another colour mode help?

No, it would be worse.

How can I work this out for myself in the future?

The only possible improvement would be to have 16-bit depth colors. You'll have to wait for GIMP 3.0...

If you've got banding, sometimes you can reduce it by applying a Gaussian blur.

When I apply a simple light to dark gradient to a large area, my experience is that some banding in inevitable. Blurring, noise, high or low resolution, duplicate layers (moved, with blending modes and opacity) . . . to some degree, it's always present. On the other hand, what appears on the monitor may not be what you get in print, often prints show less banding (I use an Epson 7600), and changing papers can make a slight difference.

Walton

I created an A4 sized canvas and made a black background layer.

On a new layer I wanted to create a large lighting effect that would use most
of the area of the canvas:

new transparent layer -> select fg to transparent radial gradient...

But I got banding.

I selected dithering, and still got banding. I used a large, circular self-created circular fuzzy "lighting brush", and tried to create the same target effect. Still got banding.

What's the solution to this?

-- bobdobbs (via www.gimpusers.com)

Hi,
forums@gimpusers.com (2010-07-28 at 0914.52 +0200):

Say you draw a monochrome gradient from back to white along 2560 pixels. You only have 256 different colors, thus you get bands 10 pixels wide. And dithering does not have a real effect in such a case.

I'm in RGB mode. The image is 2480px wide and 2794px high.

Really big image... if dithering is not helping, and some passes of Spread filter are not hidding the problem, not much you can do currently.

Also, are you sure your monitor is not the one giving you some extra banding? Some are sold as 24 bit color, but are "18 plus tricks".

Is there a way that I can create a smooth gradient?

Higher bit depth, which is not possible in GIMP for now.

GSR

I think your problem may be more to do with your computer display settings. Mines is on 32 bit - and I get no banding at all.

GSR - FR writes:

Also, are you sure your monitor is not the one giving you some extra banding? Some are sold as 24 bit color, but are "18 plus tricks".

Probably _most_ monitors sold these days are "18 plus tricks" (though the "tricks" these days seem to be a lot better than in the past), with dodgy wording in the specs used to hide that fact from all but the most determined buyers.

-Miles

You might want to check the color depth of your document. If it's indexed color then the document may not be able to create smooth gradients because their aren't enough colors in the pallet. You can tell if this is the problem (on 2.6.8) by going through the menus to image->mode->... If image->mode->indexed is selected then the document is indexed color, and you should change it to image->mode->RGB.

On 08/25/2010 02:35 AM, bob wrote:

Hi Miles.

I'm afraid the technical details of bit-depths and monitor hardware are beyond me.

However, when playing with inkscape I can create gradients that don't have bands.

Also, when I'm viewing other peoples artwork online I don't get the bands.

I'm guessing that this might mean that the problem might not be my monitor, but is more likely to be the technique that I'm using in gimp. Could this be the case?

Am 25.08.2010 08:35, schrieb bob:

Hi Miles.

I'm afraid the technical details of bit-depths and monitor hardware are beyond me.

However, when playing with inkscape I can create gradients that don't have bands.

Also, when I'm viewing other peoples artwork online I don't get the bands.

I'm guessing that this might mean that the problem might not be my monitor, but is more likely to be the technique that I'm using in gimp. Could this be the case?

Here my two cents to that topic: photographic images don't show bands, even with low bit-depths.
The reason is the noise within each photo. Bands can be avoided by introducing controlled noise:
chose the least significant bit of each pixel's channels randomly depending on the exact color of
the gradient at that point. But probably this must be a new feature within GIMP...

Joerg