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What is bit depth?

Updated: Jan 23, 2021

Bit depth refers to the color information stored in an image.

Along with an image’s resolution, the bit depth determines the size of the image. As the bit depth goes up, the size of the image also goes up because more color information has to be stored for each pixel in the image.

While an image has a bit depth, so does your display. You can change the bit depth of your monitor by accessing the display properties. Right-click on the desktop and select Properties, then click on the Settings tab. You should then see a Color quality menu where you can change the bit depth. You can also change the resolution of your display using the Settings tab. The bit depth, as well as the resolution, is actually determined by the capabilities of your graphics adapter. If you know you purchased a graphics card capable of displaying high resolutions and a high bit depth but you don’t see them as options in the Settings tab you may need to upgrade your graphics driver by downloading it from your graphics card manufacturer’s website.

So with all the talk about Log vs Lin and what can and can’t be done digitally, lets get back to the basics. Lets talk about the bit depth in color channels.

That’s right, Bit Depth. I am constantly astounded how many people here or on the Cow fail to grasp the need for more bit’s - and the misunderstanding about where and when it matters.

Let me start with a couple of basic ideas.

Color spaces are identified in the video world as either RGB or as Y’CbCr.

Bit depths are determined by how many “bits” or one’s and zero’s that are needed to identify as specific color.

So the Per Channel information looks like this.

1 bit = 2 colors ( black or white)

2 bits = 4 color (first gray-scale)

3 bits = 8 colors

4 bits = 16 colors

8 bits = 256 colors

10bits = 1024 colors

12bits = 4096 color

16bits = 65,536 colors

Do not forget that these are the numbers of colors (or levels of grey) that can be reproduced in EACH of the 3 color channels of image and they also refer to the uniquely identifiable luminance levels that can be reproduced.

So that defines the channels but what about the overall colors available are available?

Bit depth levels Total Colors Resolved

8b 256 16,777,216

10b 1024 1,073,741,824

12b 4096 68,719,476,736

16b 65536 281,474,976,710,656

The bigger issue in my mind is not everybody uses the same terminology when talking about bit depth, video uses one methodology and print uses another so this can end up being very confusing if one does not use the proper terminology for each type of workflow.

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