How many bits are raw images?

Question

1. How many bits are images taken from a camera with a proprietary format? Are they 12 bit or 16?
2. After making adjustments in ACR, do you bring the image into Photoshop at 12 or 16 bits?
Thanks.

Answer 1

web.boards wrote:
1.How many bits does the average point-and-shoot camera capture when shooting jpgs?
2. How much of a visible difference is there between 12, 14, and 16 bit raw files?
3. What do you mean by the are "opened into 8 or 16 bit precision based on the Camera Raw preferences"? Does this mean that some of the bits could be thrown away if they are opened with 8 and it was taken with 16 bits?
Thank you.
Jeff Schewe has answered the question about bit depth of the raw capture, but one must realize that noise in the image limits the effective bit depth of the capture, since it does not make sense to quantify the signal from the sensor in steps finer than the level of noise in the image. These considerations are discussed in an excellent article by Emil Martinec:
http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html#bitdepth
Some of the newer high end dSLRs offer 14 bit quantization, but the gain in levels is often negligible because of noise. P & S cameras are much noisier than high end dSLRs and their effective bit depth in terms of the number of actual levels that can be perceived in the rendered image is open to question. There is a loss of levels when one goes from a linear raw space to a gamma encoded space such as Adobe RGB. Bruce Lindbloom's levels calculator can calculate this loss. The reader should try a few values with the calculator using the bit depth of the camera and a gamma of one and a gamma of 2.2 for the aRGB. With Photoshop, use a bit depth of 8 or 15, since Adobe uses a bit depth of 8 or 15 in Photoshop, effectively halving the number of levels over what could be obtained with full 16 bit output. However, for current cameras, this is of no significance.
http://www.brucelindbloom.com/