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10/26/2015 03:51:29 PM · #1 |
Hi,
When I edit pictures with large areas of color gradients and/or quite graphic type color arrangements with gradients, I usually find ugly "steps" in the colors rather than a smooth gradient. If the area is small enough and the pictures lends itself to it, I can get around it by smudging the area with a smudge tool. But it only works in certain cases and it is very time consuming.
So here are my questions: what is this officially called, so I can read up on it and does anybody have good suggestions how to get around this problem in the first place?
Thanks for your help.
I use Gimp as my main editing program, but also use Topaz as a stand alone program and in fact find it worse in Topaz than Gimp, but it does occur in both programs.
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10/26/2015 04:54:12 PM · #2 |
This is called color banding. I most often see this if there is no noise/grain in large color areas.
Believe it or not, adding a tiny, basically imperceptible amount of noise to this area can cure it. |
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10/26/2015 05:05:42 PM · #3 |
It's usually referred to as color banding. The sources of this problem is the "bit depth" of the file being edited, and the quality of the original data. That probably doesn't make a ton of sense, so I will attempt to clarify:
- Certain images (all JPEGs, for instance) a "data depth" of 8 bits per channel. That means that for each color channel there are only 256 levels possible. When you have a blue sky, for example, the main source of information is the blue channel (duh...) and when the color changes slowly across the sky, you will see the steps.
- Even if you edit in a 16-bit-per-channel mode, if the originally acquired image lacks data depth (acquired as a JPEG, or underexposed and adjusted aggressively in post) you can end up in the same position
The steps you can take to minimize the issue (usually make it all but disappear unless you go looking for it) are:
1.) Shoot in RAW
2.) Expose to the right
3.) Process in a 16-bit space, and only save to JPEG when you need to
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10/26/2015 05:07:18 PM · #4 |
Originally posted by giantmike:
Believe it or not, adding a tiny, basically imperceptible amount of noise to this area can cure it. |
My experience is that adding the noise may hide it somewhat, but I still see it, and it still bothers the H-E-Double-Hockeysticks out of me.
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10/26/2015 05:12:53 PM · #5 |
You will also see it when there are too few shades in the gradient. You can also somewhat control it with Curves. Editing in 16-bit might help (more colors available). Banding can also appear when saving to JPEG if the image has to be excessively compressed (like to meet the DPC size limit).
Also, make sure you monitor is set to display in millions of colors. |
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10/27/2015 12:34:33 AM · #6 |
Eish ... that's a good South Africanism ... sort of hard to put into any other word ... in any case, this thread just shows again how much I DON'T know. So firstly, thank you guys for replying.
Secondly, if THIS is color banding, then what is the just as irritating thing when you get a color (usually reddish?) outline on a subject? Depending on the picture of course but just 1 or very few pixels wide? You also get it in blue. I always thought THAT was color banding ... (hanging head in shame for ignorance!)
Then my next question: I (almost) always shoot in RAW and jpg anyway. I edit the basic stuff in RAW if I think the image needs basic editing (Digital Photo Professional, which is the Canon program that comes with the camera). But most of my images I do far more extensive editing on (composits, textures etc.). Which program allows you to do that in RAW and what size processor would you need?? and can you combine RAW and jpg layers?
I will put a layer of noise over the latest image I got irritated with ;-) to see what it looks like in this case; and first try to edit it in RAW, because this particular one I actually did more on contrast/dynamics than anything else.
Thanks again for explaining.
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10/27/2015 09:17:28 AM · #7 |
Originally posted by kasaba:
...if THIS is color banding, then what is the just as irritating thing when you get a color (usually reddish?) outline on a subject? Depending on the picture of course but just 1 or very few pixels wide? You also get it in blue. I always thought THAT was color banding ... (hanging head in shame for ignorance!) |
This is most likely lateral chromatic aberration. It normally appears worse near the corners of an image, and the color fringe along one edge will be the opposite color as the fringe along the opposite edge. It is easily correctable during RAW conversion with programs such as Adobe Lightroom. There is also longitudinal CA, which is more difficult deal with; you can mitigate the effect, but not truly correct it.
Originally posted by kasaba:
Then my next question: I (almost) always shoot in RAW and jpg anyway. I edit the basic stuff in RAW if I think the image needs basic editing (Digital Photo Professional, which is the Canon program that comes with the camera). But most of my images I do far more extensive editing on (composits, textures etc.). Which program allows you to do that in RAW and what size processor would you need?? and can you combine RAW and jpg layers? |
Think of the RAW file as your "digital negative." You need to convert it to a usable form before editing. You don't save back to the RAW format, you need to keep the edited file in an editable image format. Normally, we choose JPEG for this, because it is the file format we most often want to end up with. The problem is that JPEG is stuck in the '90s, limited to 8 bits per channel. One alternative to JPEG is the TIFF format. TIFF files can be 16 bits per channel, and can even have multiple layers. They can also be very large. Another option, if you are going to do additional editing in Ps, is to use the PSD (Photoshop file) format. This option will not be available, however, if you are using the Canon software to convert your RAWs.
Everyone who shoots RAW has faced this storage conundrum... how do we avoid keeping a RAW file, a 16-bit edited file, and a final JPEG output file for every photo? We don't want to ditch our "negative," and we don't want to have to re-do all our editing to correct a minor mistake, so we really don't want to lose our intermediate (TIFF or PSD) format.
My personal solution to this is to do the vast majority of my editing in Adobe Lr (Lightroom), and only go to Ps for complex tasks involving a lot of detailed editing, layers, etc. The editing in Lr is non-destructive, that is, it does not get written to the RAW file, but exists as settings in a "sidecar" file in the same folder as the RAW file. Lr also streamlines my importing, culling, cataloging, and final image creation work paths.
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