Paul-- Scanner scan red, green and blue at a certain bit depth. Some Nikon scanners scan at 12 bits per channel. However, a lot of software can't handle more than 8 bits per channel (8x3=24 bits). When they can handle more, they usually require 16 bits per channel (16x3=48 bits). So the Nikon scanner scans at 12 bits (12x3=36) and if you want the extra bit depth it stores at 16 bits (48 bits). So the file size increases by 100% (if it is a tif for example) while information increases by 50%. While this isn't very efficient, it does allow for higher bit depth. Higher bit depth is important if you are going to do a lot of changes in your image editor. Each time you apply a curve or sharpen the image or resize the image you loose image information due to round-off errors. If you did enough of these operations your image would become poserized. If all you plan to do is to scan your image and print it, you don't need the extra bit depth, 8 is enough. Otherwise you want to start with a 16 bit scan, do as many operations as possible in 16 bit mode (because you can't do all the operations you want to in Photoshop 16 bit mode as you may need for example). Then convert and proceed. If you had a negative with an extremely high dynamic range (say a child under a tree with a white house in the background in bright sun) and a scanner with low dynamic range you would want to scan the image twice. Once to expose for the child and once to expose for the house. Let's say you could control the scan light, turn the light down for the house and turn it up for the child (actually, the scanner does this for you when you adjust the levels). Then you would combine both images into one. If you had a scanner with an extremely high dynamic range, you could scan once and have all the information you needed. The scanners that use an infrared channel (fourth channel) for surface defect detection typically don't let the user at this channel, so it doesn't come into play in the scanner's specifications. The scanner uses this information during the scan along with software to remove the effect of dust, scratches, fingerprints, etc. from the output image. As many readers on this list know, I'm biased, but I believe the most important feature is the Digital ICE (the surface defect removal), Digital ROC (Color Restoration) and Digital GEM (Grain Management). These tools really make a difference in the quality of scans. Good luck in picking a scanner! Jack Phipps Applied Science Fiction >I've just been reading some Nikon literature about their new scanners, and >I have some questions about the terminology. The ad states that the >coolscan IV ED yeilds 48 bit images (48 bits per pixel?). Later, it >states that the scanner has a color bit depth of 24 or 36 bits. What does >this refer to? It also states that the scanner has a dynamic range of >3.6. What is a scanner's dynamic range? Can anyone suggest an article >somewhere on the web or elsewhere that explains all this? Thanks.