What is posterization / banding
Posterization occurs when the color depth (bit depth) is not sufficient to sample a continuous gradation of color tone and thus, we end up with a series of (discrete) steps or bands. Unwanted posterization is called banding.
How to prevent posterization / banding
It is better to prevent posterization / banding than to deal with it. Here is how:
- Pay attention to your RGB histogram
Apparently, preventing posterization / banding when taking the shot(s) is the best solution. Especially in long exposure photography, you should be careful when shooting and always try to get the best exposure possible. Overexposure (oversaturation of any channel) lies at the very heart of posterization / banding.
- Work with more tones & use 16-bit processing
Needless to say that photographers must shoot all images in raw. Since posterization / banding is caused when little information is spread too far apart, it is absolutely essential to shoot and start your processing with raw files.
Also, edit your photos in 16-bit mode to reduce your chances of posterization / banding and don’t forget to export them into 16-bit formats with as high resolution / analysis as possible.
- Subtle post-processing
Somewhat simplistic but true. Minimising the amount of image editing and cropping, or using tools that don’t spread the tones apart (for example Brightness / Contrast instead of Curves or Levels) may be a life saver.
How to deal with posterization / banding
The problem can be solved by adding noise. Small (so it is not noticeable) amounts of noise will hide the bands and thus, the viewer can no longer detect the edges.
It is also highly advisable to experiment with (Gaussian) blur after adding noise to smudge the (remaining) color bands.
However, adding noise (that we usually try to remove) should take place after editing and cropping but before the final sharpening.
Last but not least, note that posterization / banding will be (more) visible on platforms and mediums that require (some level of) compression. This might explain why you may notice posterization / banding on a photo online but not when you print it.
Photographico | C. Sergios Photography Posterization / Banding