10.1Mp RAW and Adobe Camera RAW
 

In ACR, when I open my CR2 file, I can select op[tions at the bottom to have the image as:

Adobe RGB,
8bit or 16bit,
size (from 1024x1256 @ 1.6Mp up to 4096x6144 @ 25.2Mp),
Resolution,
Sharpening (for screen, glossy, matt)

Does my camera capture 16 bit? Should I then have this set as 16 bit?
And secondly, if I change the size setting, what effect will that have on quality? Obviously reducing the size will degrade quality as I will throw away pixels (I assume), but what about increasing it? Is there any reason to change this size up (to 4096x6144 at 25.2Mp) or am I also introducing problems. I assume I am adding (interpolating) pixels?

Does anyone sharpen at this point, with these controls?

It just seems silly to me, that if these are changed and that degrades the image, why have them? The program can still deal with any input, but there'd be no need to change those settings.

Cheers

Raw
 

2nd para first:
If your camera supports 16 bit, use it.
Shoot at the max pixel resolution that the camera offers.
Don't reduce the pixel size of your image for processing,and save it at full size as a PSD. Use the full size image for printing unless is too large for this to be sensible (see below). At 10.1 Mp, I assume that it will be about 3900 x 2600, which, at a really high resolution of 320 dpi, will give an A4 print, or an A3 at 240dpi. I always print with a resolution which will divide exactly into my printar resolution of 2880. For smaller prints the resolution would rocket up, so I keep the image res at 320 and resample accordingly, using Bicubic Sharper; there is some loss in theory , but it won't show in a smaller print. I would only ever resample upwards as a very last resort.

1st para: Adobe RGB
16 bit
Size that of your basic image (c.3900 x 2600).
Res: I put it at my main printing size for convenience, but it doesn't matter much as your can vary it later if you need to.
Don't do any sharpening here, leave it to the very last, after processing and flattening your image.

Final: Yes, down sampling does lose information, but may be necessary. For projection, the usual size is limited by the capability of the projector and most commonly needs to be a maximum of 1024 pixels horizonal, and 768 vertical. This should be saved as a jpeg and using the highest quality setting of 12. The same sort of limits apply to images for web transmission, and the profile should be changed from Adobe RGB to srgb. You can't save a 16 bit image as jpg so you'll have to change to 8 bit before saving.