by Medley on Tue Jul 10, 2007 6:29 am
A very good article, and Deke McClelland is one of the best in the world when it comes to all things Photoshop. He's been at it for a very long time- the man WROTE the Photoshop 6.0 Bible. But there is a very pracitcal use for Photoshop's 16 bit mode.
8-bit images have 256 tones (or levels) possible in each of the red, green, and blue channels. But most Digital SLRs on the market today are capable of capturing 12 levels, or 4096 tones in each channel. Images captured in the camera's RAW format are imported in 16-bit mode, and have all of this information available. Yet the human eye can only differentiate about 200 tones, so the 8-bit image and the 16 bit image will "look" identical. So what's the big deal, right?
The difference becomes clear when you realize that 90% of the commands that you perform in Photoshop discard information. The commands that affect the entire image, such as Levels, Curves, or Shadow/Highlight discard the most. The more commands you use, the more data that gets discarded. So while the eye can't tell the difference between 4096 levels and 256, it CAN tell the difference between 1000 levels and, say, 64.
That's the payoff. Images that start as 16 bit images give you a LOT of room to process in Photoshop before the image begins to break down, and 8 bit images give you very little.
Also, converting an 8-bit image to 16-bit mode accomplishes nothing. You can't "add" data to an image, you can only lose it. That's why shooting in RAW format has become so popular.
Hope this helps.
- Joe U.
There are only 10 types of people in this world- those who understand binary, and those who don't.
