what bit depth to scan at?

Is there any reason to scan color transparencies at 48 bit over 24 bit? What is the best way to scan B&W film- at 16bit greyscale, or as 24 bit/ 48 bit color, then convert it to greyscale? Or scan in 48 bit RGB and use only the green channel (thought I read that once)?

I am scanning MF frames (6x6), 4x5, and 5x7 sheet film, with max enlargement to 16x20.

Thanks,
Tim

Depends on your ultimate use. For the best quality on the "keepers", scan the color trannies at 16 bit/channel (48 bit). My POV has always been--for the keepers--scan once to extract all the info you possibly can from the original, then repurpose the file as needed for various applications. Scanning is by far the slowest and most tedious part of the film-to-digital workflow, so who wants to have to redo it?

For B&W film, I see no reason to scan as RGB, since each channel is recording the exact same information from a monochrome original; and since RGB files will be much larger than grayscale files, to no advantage. Just scan in 16 bit grayscale. If you have a software program (like PhotoKit Sharpener the PS plugin, for instance) that requires an RGB file to operate, you can simply change to RGB and PS will build 3 identical channels from the single grayscale one.

For those you don't think are keepers, 8 bit scanning at low resolution is fine.