First off color depth is really shades of one color. Whether 8, 12, or 16 bits you are still talking about the shades of the color from white (no color) to black (100% color). The difference is how many shades you can divide it up into. Is that clear?
Second colors (as on the screen) is a combination of all the color channels. They are talking about, for instance, 3 channels of 8 bits each (64^3) = 262144 (so called) colors, or 256K in octal(base8).
Now when your expand your file from say the 12 bits (from the camera) to 16 bits (in photoshop) all you are doing is taking that 256 shades of one color and filling in (by interpolation) the blanks with calculated intermediate values.
The 12bits in the camera is simply padded out to 16 bits because our computers these days are all based upon module-8 (that was not always so back when they were made up of discrete components). That is the 16 bits have ************xxxx values (where the * indicate data bits, and the x indicate no data (padding) bits).
graywolf http://www.graywolfphoto.com
"Idiot Proof" <==> "Expert Proof"
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Don Sanderson wrote:
(Warning to scientific types: Some numbers are rounded to keep me reasonably sane)
A .PEF (12bit) file is ~12MB or ~2B per pixel. A .TIF file (16bit) is ~36MB or ~6B per pixel. A .TIF file (8bit) is ~18MB or ~3B per pixel.
**If this is correct so far continue, if not stop and correct me.
Without further processing: 8 bits can describe 256 colors. 12 bits can describe 4096 colors. 16 bits can describe 65536 colors.
**If this is correct so far continue, if not stop and correct me.
.PEF files use 2B per pixel because you have to use 2Bytes to store the 12bits. .PEF files open in PS CS as 16bit files because they ARE 16bit files. PS CS can save these .PEF files as 8bit or 16bit .TIF files. PS Elements can ONLY open and save .TIF files in 8bit.
**If this is correct so far continue, if not stop and correct me.
I am running my monitor at 32bit color depth, that's over 32 million possible colors.
**If this is correct so far continue, if not stop and correct me.
Irfanview tells me my 8bit .TIF file contains 910727 unique colors. Irfanview tells me my 16bit .TIF file contains 909879 unique colors. Both these files were created from a .PEF file in PS CS, the .PEF file was imported into CS "as is" using the CS converter. It was then saved as 8 bit and 16 bit .TIFs from CS with no manipulation of any kind.
WARNING: **Now for the "Dumb Don" questions:**
1.) If the "D" has only 12 bits to describe each pixel, where do all these thousands of colors come from? I know each pixel is one color, is it the *converter* that figures out from adjacent pixel information how to determine the color of EACH pixel to a resolution of many thousands of colors?
2.) I didn't know till today that PS Elements was using only 8 bit .TIFs. Irfanview indicates that for this particular file 8 bits holds MORE color info than the 16 bit version. Why/How?
3.) Obviously an "8 bit" .TIF file resolves far more than 8 bits (256 colors) per pixel and must use all of the 24 bits alloted to each pixel to do this. (I realise these bits store other info as well.) So what is the distinction between an 8 bit and 16 bit .TIF? Would these more accurately be called 24bit and 48bit .TIFs? Or is this more an indication of the platform and software requirements than the file structure?
I think I've answered a lot of my own questions by typing this all out but I'd still like some clarification or correction to my jumbled thoughts. ;-)
TIA Don (NOW, for dinner and a few aspirin......)
