Monday, March 23, 2009

Bit depth

I'm back from the NATIA conference and will (hopefully) get to everyone's e-mails.

The term "bit depth" is used to describe the number of possible colour values a pixel can have. This concept confuses some folks and I tend to get a quite a few questions from folks who have trouble grasping this rather obscure topic.

Here's a way of thinking about it:

Bit depth = 1
Two possible values: black/white

Bit depth = 8
2 to the 8th power = 256

When you come across a different bit depth, think 2 to the power of the number of bits and you'll have an easy way of figuring out the number of possible values.

Here's a quick quiz. How many possible colour values for a bit depth of 12? Now, how many for 12 bits per channel RGB? If you are shooting in RAW, and your images are 12-14 bpc - would you want to try to cram that info into an 8bpc RGB image out of the gate? Most assign the image a 16 bpc working space in ACR and give the image some head room.

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