"....When I import pics from my camera and open them in PS (CS4) the document size automatically defaults to 48x32...and pixel dimensions are 22.8M (3456px x 2304). Is there something I should be doing to get smaller images?"
In it's native state, your camera produces a "perfec
t" 4 x 6 image as stated above by the rest of the folks. If you sent your file, as is, to your print shop you would get back a 4 x 6 image regardless of what the document size says it is. Depending how you have your camera's resolution set can and will change the file size, but that effects resolution, and not the 4 x 6 dimensions. Being that 4 x 6 is the aspect ratio, you can produce any size enlargement that is a multiple of 4 x 6 without losing any of the image..8 x 12's, 12 x W's, 16 x W's, etc. Obviously, neither 5 x 7, 8 x 10, nor 11 x14's are multiples of the native aspect ratio. With those crops, you will lose some part of the image. Hope this helps, and does not confuse more.
Vinnie