An Effective Way To Remove Banding That’s Not Adding Noise
Ask any retoucher what their number one nemesis is and they’ll probably say “Banding!”, those curving lines separating each band of color as the tones go from light to dark. These bands are caused when each step in color stands there screaming for attention. They taunt us while we endlessly work to chase them away.
Kind of like this:
The image above is cropped from the upper left corner of the shot below, which is a lifestyle shot I worked on a couple of years ago.
The banding appeared in the last stage of the retouching when the color grading treatment was added to the image, mostly due to a Curves Adjustment Layer set to Soft Light blending.
This is an enemy we’ve have been fighting for years, going back to the very early days of digital retouching. Basically, they appear when there are too few color steps available in going from one color to another. In the example above the gradation from dark to light is what’s causing the problem.
Because this pretty much comes down to a math problem, blurring doesn’t help, so we’ve had to resort to other tricks to defeat this foe. Usually this has been some form of adding Noise which helps to break up the borders between the colors making the banding harder to see.
The problem is often most visible or exacerbated when working in 8-bit, and again, since this is basically a math quandary many would say “You should have been working in 16 bits all along!” but alas here we were, right at the final step when we’re getting bitten by that 8 bit banding bug. Too late for such a simple fix, right? Maybe not!
You see, my friends Joseph Merkens and Carolyn Winslow showed me a trick when I worked on a project with them. While most would say it’s too late to gain anything by converting the file from 8 bits to 16 bits per channel they had shown me that banding can often be solved by converting your 8 bit layered file to 16 bits before flattening.
So take the layered file–complete with all the adjustment and vignetting layers–and convert it from 8 bits to 16 bits. At first there may be no difference. Zooming into a 100% view gave will often show a nice smooth image, but any other view often brings back those vicious bands. However, once the file is flattened, Voila! the bands disappeared, vanquished by the coolest, easiest trick of all.
Here is that same crop after I passed the layered file through the 8 to 16 bit conversion in Photoshop:
This coolness works because as Photoshop converts the file from 8 bits per channel to 16 bits it adds just enough dithering to break up those bands. But while we’re looking at the layered file Photoshop still gets hung up in the way it draws the image on the screen. Flattening the image completes the process and makes it much easier for Photoshop to reveal the nice smooth gradations we wanted all along.