How Are Bits Used in Digital Photography?

A couple admires a printed photo.
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Bits are used in computers to assign small pieces of information into a language that the user can read. Just as bits are the basic blocks used in your computer, they are used in digital photography to capture a picture.

What Is a Bit?

A "bit" is a term originally used in computer terminology, where it stands for "binary device," and refers to the smallest piece of information. It has a value of either 0 or 1.

In digital photography, 0 is assigned to black and 1 to white.

In binary language (base-2), "10" is equal to 2 in base-10, and "101" is equal to 5 in base-10.

How Bits Record Color

Users of digital editing programs, such as Adobe Photoshop, will be familiar with different value bit images. One of the most common is an 8-bit image, which has 256 available tones, ranging from "00000000" (value number 0 or black) to "11111111" (value number 255 or white).

Notice that there are 8 numbers in each of those sequences. This is because 8 bits equal one byte and one byte can represent 256 different states (or colors). Therefore, by switching the combination of those 1's and 0's in the bit sequence, the computer can create one of 256 variants of color (2^8th power - '2' coming from the binary code of 1's and 0's).

Understanding 8-Bit, 24-Bit, and 12- or 16-Bit

JPEG images are often referred to as 24-bit images. This is because this file format can store up to 8 bits of data in each of their three color channels (RGB or red, green, and blue).

Higher bit rates such as 12- or 16-bit are used in many DSLRs to create a more dynamic range of colors. A 16-bit image can have 65,653 levels of color information (2^16th power) and a 12-bit image can have 4,096 levels (2^12th power)

DSLRs use most of the tones on the brightest stops, which leaves very few tones for the darkest stops (where the human eye is at its most sensitive). Even a 16-bit image, for instance, will only have 16 tones to describe the darkest stop in the photo. The brightest stop, in comparison, will have 32,768 tones!

About Printing Black and White Images

The average inkjet printer works on the 8-bit scale as well. When printing black and white images on your inkjet, be sure not to set it to print using only the black inks (grayscale printing).

This is a great way to save ink when printing out text, but it will not produce a good photo print.

The average printer has one, maybe 2, black ink cartridges and 3 color cartridges (in CMYK). The computer transmits the data of an image to be printed using those 256 variants of color.

If you were to rely on only the black ink cartridges to handle that range, the details of the picture would be lost and gradients would not be printed correctly. It simply cannot produce 256 variants using a single cartridge.

Even though the black and white photograph is an absence of color, it still relies on those very fine-tuned 8-bit color channels to form all of the different tones of black, gray, and white.

This reliance on color channels is important for any photographer to understand if they want a digital photograph with the look of a black and white photograph that was produced by film and paper.