In this short article, I am going to cover how to easily deal with colour banding in your digital images, with a couple of techniques for removing banding using Photoshop.
Colour banding occurs in photographs when there are only minor differences in the gradient across an area of the photograph. It typically occurs in 16-bit or 8-bit images but is more prevalent in 8-bit as there are fewer tones for your display/monitor to choose from. It rarely occurs in images directly from your camera, it is more often introduced when we post-process our images in programs like Photoshop, Lightroom, or Luminar.
To illustrate the issue with banding, I created a gradient in Photoshop and then pushed and pulled the levels. Nothing extreme, I just increased the mid-tones, and then reduced them back to their original settings. The result is that you can clearly see ugly banding artefacts across the image (Figure 1).
Fortunately, there are some simple steps you can take to reduce and even eliminate this banding from your images. I will cover these in this short article.
Removing Colour Banding – Let there be noise!
The first technique we can use to remove banding using Photoshop is to add another artefact to our image. Yes, this sounds counter-intuitive at first, because intuition says we want to avoid artefacts in our images. However, by adding just a little noise, say 1 or 2% to our image, it has the effect of breaking up the areas of the image where there are only small changes in gradient and therefore makes it easier for our display to resolve the image without any banding. So essentially we are adding one artefact which is barely noticeable, and in so doing, removing the ugly banding artefact.
With your image open in Photoshop, select “Filter” from the top menu, then “Noise”, “Add Noise”. A pop-up window appears, see Figure 2.
You can experiment yourself with whether a uniform or Gaussian distribution of noise works best for your image, but either way, I tend to use either 1 or 2%, then click OK. In our example (Figure 3), you can see that the banding has not been completely eliminated, but it is much less noticeable.
In the introduction for this article, I alluded to 8-bit images having fewer tones than 16-bit. Essentially then, by increasing the resolution of your image to 16-bit, then your display has more tonal variances to work with, and therefore a better chance of displaying gradients without the banding artefact.
You may be asking yourself why I didn’t use this technique instead of adding noise. Well, the technique will only work if your monitor can resolve these tonal differences, i.e. you could set the image to 32-bit to give you even more tonal variations etc, but if you only have a 16-bit monitor, you are wasting your time.
Anyhow, assuming you are using a 16-bit or higher monitor, let’s open our image in Photoshop, and then click “Image”, then “Mode”, then select “16 Bits/Channel”. When you then save your image, it will have been converted to 16-bit.
Again, this technique may not (depending on your image) remove all banding artefacts from your image
Both of these techniques are something you can easily do if you find you have banding artefacts, you can even apply both to the same image! Also, with the technique for adding noise, you can, if you wish, apply selective noise to the affected area. For example by masking the foreground, and then only applying the noise to the background.
If this article was useful to you, please take a look at our other Learn Photography guides.
Here are some other Photoshop articles that may be of interest to you:Photoshop Articles
References – Wikipedia
Specialising in landscape and wildlife photography, David is a semi-professional photographer based in Scotland, with an established fine art and stock photography portfolio; which includes published photography with the New York Post, Huffington Post, as well as various travel and tourism companies worldwide.