Understanding Bit Depth in Image Files

Terms like 8-bit, 10-bit, and 14-bit are commonly used in camera forums. But do you understand what bit depth really is and how it affects images? Here’s a short video from ZY Productions explaining everything you need to know about bit depth:

Bit depth (not to be confused with bit rate) relates to the amount of color information in an image. The greater the bit depth, the greater the color information stored in that image.

“The more bits you have, the more shades of grey you can record or display.”

For simplicity, imagine a gradient that transitions from pure black to pure white. Everything in between is a shade of grey. A greater bit depth would mean that there are┬ámore “steps” from black to white (i.e. the transition is very smooth).

image with high bit depth

Notice how the transition among various shades is relatively smooth in this example with high bit depth.

On the contrary, if the bit depth is low, it will have less information and hence the transition will not be as smooth.

image with low bit depth

The transition among various shades is not so smooth in this image with low bit depth.

Calculating the number of shades of grey contained by a particular bit depth is quite easy. If the bit depth is represented by n, then the total number of shades of grey would be 2n. For instance, an 8-bit image means that it can have 28 = 256 shades of grey. And a 10-bit image can contain 1024 shades of grey. Notice what seems like a difference of 2-bits actually has a difference of 4 times the information.

Generally speaking, whenever we say 8-bit or 10-bit, it refers to bits per channel (BPC). A color image is comprised of three channels: red, green, and blue. Therefore, an 8-bit color image will have 8 bits of red, 8 bits of green, and 8 bits of blue color information, which makes 24-bits of color information.

Typically, cameras take JPEG images and videos at 8-bit. However, photos shot in RAW have 14-bits of information per channel. This is the reason why we can play around with so much data in post-processing using RAW images. Isn’t this information enough to start shooting in RAW (if you haven’t been doing so)?

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