Today’s Question: Do all cameras have approximately the same bit depth or do they differ significantly? If so what is the difference?
Tim’s Quick Answer: Most cameras today provide 14-bit per channel analog to digital conversion. A small number of higher-end cameras offer 16-bit per channel support, and some (mostly older) cameras are limited to 12-bit per channel. Cameras with higher bit depth have the potential for greater detail with smoother gradations.
More Detail: Light represents an analog signal, and so you could say that light could theoretically be divided into an infinite number of brightness values. However, digital images are described with discrete numeric values, and so a limit to how many values are available must be defined.
You can think of this limit as being a limit to how many digits can be used for a number. If you are limited to a two-digit number, the maximum value is 99. For a three-digit number the maximum value would be 999.
In the context of digital images, bit depth defines the limit in terms of how many possible values are available, and therefore how many tonal and color values are possible. Cameras that only offered 12-bit per channel analog-to-digital (A/D) conversion were limited to a total of 4,096 tonal values per channel, or more than 68 billion possible tonal and color values for a full-color image.
Most cameras employ 14-bit per channel A/D conversion, providing 16,384 tonal values per channel, or more than 4 trillion possible tonal and color values overall. And those few cameras that offer 16-bit per channel A/D conversion offer 65,536 tonal values per channel, or over 281 trillion possible tonal and color values.
Of course, you only really need about 8-bit per channel information to provide a photographic image of excellent quality. But having more information can ensure you retain smooth gradations and optimal overall quality, even after strong adjustments are applied. So there is an advantage to higher bit depth, but that advantage has a diminishing return.
When processing your images after the capture, most software only provides support for 8-bit per channel and 16-bit per channel modes. So when your camera “only” offers 14-bit (or 12-bit) A/D conversion, you would still generally be working with that image in the 16-bit per channel mode. You simply don’t have full 16-bit information in that scenario.
I wouldn’t recommend choosing a specific camera based only on the bit depth of the A/D conversion for that camera. Many other factors are far more important both in terms of image quality and overall feature set. All things considered, I would say that most cameras today are about equal in terms of the net effect of their bit depth, in large part because the vast majority of cameras today offer the same 14-bit per channel A/D conversion.