April 21, 2014

post-processing workflow: how to deal with color banding / posterization

If you’ve ever noticed banding or  posterization in your photos, where you’d expect solid colors, then there’s a relatively easy fix for it. This posterization effect appears as bands of colors, where the transitions between similar tones aren’t smooth, but have jagged edges instead.

It is caused by the 8-bit JPG not having enough data to give you a smooth gradient when large blocks of color slowly change. You’ll often see it in the blue sky in landscapes, or as in this case, with large areas of color in the background. Actually, the image above doesn’t show this – I fixed it. Here’s how.

1. Working with the 8-bit JPG from the start. You can see that blocky posterization happening therein this 100% crop. This is typically what the color banding looks like – as seen is this 100% crop from the image above. The even tones are broken up.

The trick is to not convert your edited RAW file immediately into JPG. Instead, process your RAW file as a TIFF, or as DNG, which are 16-bit (or higher).

2. The 16-bit TIFF version, converted to JPG only as the final stage, shows reduced banding. In saving for web, the banding is slightly re-introduced but at a lesser extent than working with just a JPG originally. The DNG version also reduced the banding.

 

working first with a 16-bit image rather than an 8-bit JPG

For most of my usual workflow, I edited the RAW files for Exposure, WB, Contrast and such. The main adjustments (and any heavy lifting) is done with the RAW file which use 12 bits or more, for data. This is obviously a lot more data than an 8-bit JPG has. Then I do finer retouching such as skin retouching, on the JPGs. When you then save and re-open the JPGs, this kind of banding becomes noticeable with some images.

When I work with images that show this kind of banding, I change my workflow. Instead of converting the edited RAW file to JPG, I convert to 16-bit TIFF instead, and then do the retouching. Only at the final stage, do I convert to JPG for web use, or for uploading to a lab. In this way, I work with a 16-bit file for as long as possible.

Lightroom’s latest incarnation allows you to do retouching on the RAW file, so that side-steps much of this altogether.

That’s essentially it – avoid the 8-bit JPG step as far as you can in your workflow. This will greatly reduce the chances of seeing this kind of color banding.  As if you needed more reason to shoot in RAW!

Of course, since this is Photoshop, I am sure there are other ways of dealing with this. If you have another method that works, let us know.

 

lighting setup & techie details of the main photo

Above is the (nearly) original image, not cropped to a square format. I have to say “nearly” because I missed the composition while shooting in the studio. I chopped a fingertip off.

I really liked Anita’s pose here. So I cloned in the fingertip in from another finger in Photoshop. And then finessed the extra width of the image via Photoshop’s Content Aware Fill. Whoever at Adobe came up with Content-Aware Fill, is a genius. Also, whoever devised the Healing Tool, should be nominated for a Nobel Prize for awesomeness.

 

The colored lights are from two speedlights in the background, with colored gels over them.

 

equipment used during this photo session

  • camera settings: 1/200 @ f/4 @ 200 ISO

 

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{ 12 comments. } Add a Comment

1 Trev April 21, 2014 at 3:31 am

As Neil pointed out, converting your RAW file by exporting out as PSD/TIF/DNG in 16-bit mode is what is needed to stop banding.

If doing basic edits in your RAW Convertor especially a large contrast range in say sky, there are two options actually you can try.

1) Export out first of all by converting the RAW to either of the 3 formats I mentioned and in 16-bit mode, then editing, save the jpeg, then convert to 8-bit.

2) If you do a large volume of edits say in a wedding, and you automatically export out the basic edited file to your preferred format in 16-bit, the file sizes will almost double in file size, take almost twice as long to export and longer to open, so my method is to export all out as 8-bit first since I don’t add any contrast initially, only WB and Exposure, even sharpening I leave until I am in photoshop so I can mask the red channel for the faces, being primarily a wedding photographer.

So my preferred method is then to just export out as 8-bit, and as I am editing and I see an image which I know will have problematic banding, I will convert it 16-bit, edit, save as jpeg, then convert back to 8-bit. There is no difference in exporting to TIF or PSD, you will get the same result. (I’ve never bothered with DNG)

Obviously you can export out initially to a full 16-bit file, if only working with a few files, but when I want to do major work in photoshop on a lot of images as I do, I export out as 8-bit PSDs, quick click on action to convert to 16-bit as I see fit, do the edit, finish, flatten then save as jpeg, and convert back to 8-bit which obviously is needed to print the files.

The reason I don’t export out a lot to 16-bit is because the file sizes are enormous and with lots of files, it soon adds up. eg: a file I tested when exported out as 16-bit was 70Mb, but the same file as 8-bit was 34Mb – a bit over double file size, which takes as I said longer to export, and longer to open in Photoshop.

Also, it’s not a lot of images I am having to deal with for banding, so it’s pointless converting all to 16-bit first up, then having to convert back, running any actions on 16-bit files as I do takes almost double the time, and over hundreds of images, those extra 10-20 seconds add up very quickly.

Now it’s not only with JPG in 8-bit which causes the banding, it’s because in JPG format the shadows and highlights are soooo compressed, and lots of data is thrown away which would include those delicate highlights you want, along with the nice even shadows tonal range.

In RAW, as you know, they are retained, and when done right, you won’t get the banding/posturisation.

Finally, you must make sure on exporting that you actually choose 16-bit file size, if you want to go the initial path of exporting out straight up to 16-bit. In ACR and Lightroom, the options are there.

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2 Brad Barr April 21, 2014 at 10:11 am

Couple other ways…esp if you already/only have the jpeg with the artifacts….a quick solution that works well if the problem areas are sky or simply backgrounds with little detail. 1. Dupe the layer, 2 apply small amt of Filter>Surface blur then 3 apply a quick mask, and 4 paint off the blur from all the non-affected areas.

Interestingly, on Nikon cameras, you get this a LOT when shooting “normal” jpegs, but very little when using “fine” jpegs. Of course the raw workflow above will eliminate it even further, although I haven’t really had to do that to avoid this phenomena.

Cheers!

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3 Frank Palmeri April 21, 2014 at 10:33 am

Neil, I have to shake my head and smile virtually everytime I use the Content-Aware feature on Photoshop’s various tools. It simply is remarkable!!

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4 Jo Craig April 21, 2014 at 7:10 pm

This is really useful info, thanks. I face this problem when I add a gradient to an image. In the past I have added a noise pattern over the affected areas, just enough to fix the banding but so the noise is not noticeable. Next time I will try working on a tiff file instead, thanks for the tip!

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5 Trev April 21, 2014 at 8:17 pm

Hi Jo,

Just make sure the file is 16-bit, that’s the important part and not just because it is a TIF, check the settings when exporting out. Just thought I would mention that, since no matter the format (apart from jpeg) you will still have banding when adding contrast to large blank blocks of color like sky PSD/TIF/DNG if still in 8-bit.

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6 Jo Craig April 21, 2014 at 9:01 pm

Yup I export from Nikon software and I recall the tiff settings. Thanks Trev.

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7 oscar April 21, 2014 at 9:52 pm

Great tip! And I gotta say, the photograph you create at top is absolutely stunning!

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8 ZullU April 22, 2014 at 3:15 am

I am having serious banding issues when creating a gradient from grey to a light grey (from scratch) and yes I am working in RGB 16bit. The only fix is ADD NOISE :( but I hate noise. I know that banding appears when there is not enough information requiered to show a smooth transition but still … can someone pls tell me another workaround that doesn’t add noise?

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9 Colin Cruickshank April 22, 2014 at 3:44 am

Yes it’s a problem I have had especially when using OCF and under exposing the sky by a couple of stops – I have in the past added monochromatic noise to prevent the posterisation. One thing I have found that helps images uploaded to Facebook is to convert them to PNG’s rather than JPEG’s as Facebook can’t compress PNG’s anywhere as much!

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10 Johan April 22, 2014 at 9:41 pm

Worth a try. Tut by Lee Varis: http://m.youtube.com/watch?v=HLWh68q_yUI

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11 stefaan May 1, 2014 at 3:35 pm

Dear ,

I have a question where can i order this beautiful piece of dress?

Gr Stefaan

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12 Neil vN May 1, 2014 at 4:47 pm

You’d have to contact Anita De Bauch, the model: Facebook page  / website

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