Bit depth is something we hear spoken of a lot. When the Panasonic GH5 was announced with the ability to shoot 10Bit video, a lot of people went kinda loopy. Equally as anticipated now is the Blackmagic Pocket Cinema Camera 4K’s 12Bit RAW CinemaDNG.
But what is it? And what does it mean in real terms for your footage or images? Well, the guys at the Videomaker channel on YouTube have your back, and they’re here to explain in this 3-minute video.
Essentially, it boils down to the number of colours and shades of a colour that can be stored in the image. The bit depth is noted in binary digits (bits), and relates to how many different brightness levels are available in each of the three red, green and blue colour channels.
So, in an 8Bit image, each of the red, green and blue colour channels has 256 possible values for a total of around 16.7 million colours. Human vision can only see around 10 million colours, so isn’t this enough? Well, while the human eye can see around 10 million colours, they aren’t necessarily the same 10 million colours picked up in an 8Bit file.
There are subtle shades and colours in between them that our eyes notice but that 8Bit images simply can’t reproduce. This is why we often see banding in gradients like skies. Increasing the bit depth from 8 to 10Bit only increases the file size by about 20%, but it increases that 16.7 million colour range to over a billion. And when you step up to 12Bit video, that’s 68 billion possible colours that the camera can record in your work.
The other advantage of having a greater bit depth is that it gives you more latitude in post. And I’m not just talking about “fixing” shots, either (although it will help with that). I’m just talking about simple colour grading.
If you load an 8Bit image into Photoshop and start adding adjustment layers, it’s going to break down very quickly. And when you recompress it and save it back out as a jpg, it’s going to lose even more data. Starting off with a 10Bit or 12Bit file means that it won’t degrade so quickly while you’re editing it, and the compression algorithms have more original information to work with when saving out.
While the video above is tailored more towards video, the same holds true for stills. This is why we’ve seen the progression from 10Bit RAW files to 12Bit, with 14Bit now the standard amongst most medium-to-high end DSLRs and mirrorless cameras. 14Bit, by the way, can contain over 4 trillion different colours and shades.
Many of the Phase One and Hasselblad medium format cameras are 16Bit per channel. That’s 281 trillion possible colours. Now you know why people go on about their tonal reproduction. That’s only twice the size of an 8Bit file, but containing around 240,000 times as much information.
You do, of course, typically need a more powerful computer to work with higher bit depth files. But computers are getting faster and cheaper every day.
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