Bit depth is data. The higher the bit depth the more information a photo contains. High-bit depth images have more color. They are more resilient during exposure and color edits. Here are the inside details on bit depth.
What is a bit?
One bit is one-eighth of a byte. Bytes contain eight bits. A single bit is either a one or a zero.
Bit depth in depth
Bit depth in photographs is either 8-bit, 16-bit or 32-bit. The higher the bit depth, the more information in the file. Let’s start with the most basic file: a JPEG.
Every digital photograph has three channels of color: Red, green and blue. In a JPEG, each color channel has 8-bits. An 8-bit channel has 256 tones including black and white. It doesn’t seem like much but when the three channels are multiplied by each other, they yield over 16 million colors!
In a byte, each bit has an on state or 1 and an off state or 0. This has a bit depth of 1. Photographically 1 is white while 0 is black.
Bit depth expands exponentially as shown below.
JPEGs and bit depth
A JPEG file has 256 tones per RGB channel. It is perfect for printing and displaying on websites. Currently, the best printers and monitors can reproduce the color space JPEGs contain. It’s usually sRGB. I think of JPEGs as an output-only file. I almost never shoot JPEGs with my camera.
JPEGs suffer when big changes in editing happen. For example, I created these three JPEGs from the original RAW file. I set the color temperature to tungsten in Camera Raw then saved it as an 8-bit JPEG*. The first photo is super blue. Next, I used the Camera Raw filter in Photoshop to warm it to where it looks more like daylight. Compare it to the JPEG of the original capture.
*JPEGs are 8-bit only.
Editing the blue JPEG to look warmer just doesn’t work very well. Compare the center photo to the one on the right.
Higher bit depth = more headroom for editing
There are three bit depths highlighted in yellow. These are capture bit depths. The greater number of tones in these bit depths gives more leeway in postproduction.
16-bit captures are the realm of the super pricey medium format cameras like Phase One and Hasselblad. DSLR and mirrorless cameras capture in around 14-bits. My Canon R5 captures 14 bits when shooting 8 frames per second or lower. Otherwise, it takes 13-bit images. Still, 13-bits is 32 times more data than an 8-bit JPEG.
32-bit HDR
The high end of bit depth is HDR — high dynamic range. Combining three bracketed images in Lightroom or Camera Raw in Photoshop or Bridge yields a 32-bit per channel DNG file. There are many editing options in Photoshop for 32 BPC files though not as many as for 8-bit or 16-bit photos. Learn more on this help page from Adobe.
