Camera Bit Depth


Today’s Question: I just learned that my camera is actually capturing in 14-bits per channel when I shoot RAW, while I’ve been working in 16-bits in Photoshop. How much detail am I missing because my camera doesn’t support 16-bits?

Tim’s Quick Answer: Most digital cameras do perform the conversion of analog information (light) to digital information (pixel values) at a bit depth of 14-bits per channel. While most software provides a 16-bit per channel mode as the “high bit” option, the difference isn’t something you really need to be too concerned with.

More Detail: With most imaging software you have the option to work in either the 8-bit per channel mode or the 16-bit per channel mode. The primary advantage of a higher bit depth is that you have a wider range of tonal and color values available for the images. This is especially important with images that require relatively strong adjustments. The greater bit depth provides more overhead so that even with strong adjustments to the image there will be enough information “left over” to ensure smooth gradations of tone and color in the image. In other words, you’ll avoid posterization.

While the high bit depth option is generally a 16-bit per channel option, you can think of this as simply being a container that allows for more than 8-bit per channel information. Some cameras convert data at 12-bits per channel, most convert the data at 14-bits per channel, and a few actually process the data at a full 16-bits per channel. However, the differences aren’t as critical as they might seem.

The 8-bit per channel mode provides 256 tonal values per channel, which translates to almost 16.8 million possible color values. It so happens that this is the number of color values that the human visual system is estimated to be able to perceive, for someone with normal vision. So it would be fair to say that for the final image, 8-bits per channel is all you really need.

However, again, a higher bit depth can be very helpful, especially when strong adjustments will be applied to the image. By starting with more color and tonal values than you actually need, you’ll still have enough color and tonal values in the image even after adjustments have been applied, so that smooth gradations of tone and color will be preserved.

For a typical image with typical adjustments, however, that doesn’t mean you actually need the full range of color values provided by a bit depth of 16 bits per channel.

At a bit depth of 16-bits per channel you have 65,536 shades of gray available per channel, for a total of over 281 trillion possible color values. That is far more color and tonal values than you ever truly need in a photographic image, considering the capabilities of human vision.

At 14-bits per channel there are still 16,384 shades of gray per channel, for a total of over 4 trillion possible color values. And even at “only” 12-bits per channel there are 4,096 shades of gray per channel, for a total of over 68 billion possible color values.

So, the bottom line is that while an analog-to-digital conversion performed at 16 bits per channel will provide more possible color and tonal values in the image, there is a diminishing return relative to the final presentation of the image. In other words, there’s no reason to have any concerns about the fact that your digital camera performs the analog-to-digital conversion at “only” 14-bits per channel.