Years ago, I read a blog entry about a photographer whose style included the "reduction of the complexity of colors" in the portraits that she took. It somewhat involved taking the three primary colors in an image and scaling back one of them until it was essentially two. Obviously, it wasn't just "turning off blue". That would make the image look weird.

It's somewhat difficult to describe objectively what this was like but I made an analogy at the time that if we took it down to one primary color it would essentially be monochrome.

I would think this can be rolled into the term color grading but the technique was quite specific. It also looked very different from split toning.

Does this ring a bell for anyone? Is this a common technique?

  • \$\begingroup\$ Channel attenuation? \$\endgroup\$ Nov 21, 2018 at 21:59
  • 1
    \$\begingroup\$ Posterization ? \$\endgroup\$
    – xiota
    Nov 21, 2018 at 23:06

2 Answers 2


This may be called decreasing color depth, reducing the bit depth or reducing the number of color planes (for bitmaps, in particular). GIF images, for example, may have only 8-bit (256 level) color, "JPEG 2000 supports any bit depth, such as 16- and 32-bit floating point pixel images." Decreasing color depth, carried to extreme, produces poster-like images, which may show banding where colors had gradations.

To reduce the color depth, try a tool such as the free IrfanView, shown below. In addition, converting to grayscale effectively removes all color information: only a single channel is used.

IrfanView decrease color depth


Duotone, monotone?

I can spam you to some tutorials I've posted:

Preparing design for duotone printing?

Printing photographs when job is a 2 spot color job

But probably you are referring to posterization. This is when you have very contrasting colors, the most typical example is the Che Guevara image on a T-shirt or Andy Warhol images of Marylin Monroe (But these ones have a colorization after the posterization)


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