Digital BW, The Print

Nick writes:

> ... he would work on the photo in 8-bit, and only
> convert it back into 16-bit for the actual printing.

Converting an 8-bit image to 16-bit just before printing accomplishes
absolutely nothing, except to take up more memory and time.  Once you've
converted to 8-bit, all the 16-bit data is lost, and you won't get it back
again by converting back to 16-bit.  It's a one way street.

> In other words, he didn't/doesn't seem to feel that
> it makes much difference which you work in - 8 or 16 bit -
> the prints seem  to come out just as good in the
> final result.

He has it backwards.  You should do as much as possible in 16-bit, and then
convert to 8-bit only just before printing (if at all), and not the other
way around.

The advantage?  Sixteen-bit files give you a lot more headroom for
manipulation.  For every gray level in an 8-bit file, there are 256
intermediate gray levels in a 16-bit file; so if you want to expand three
gray levels to cover the entire black-to-white range in an image, you can do
it with a 16-bit file and get smooth results, but if you do it with an 8-bit
file, you'll get huge posterization, with only three shades of gray
throughout the image.

I try to stay in 16-bit for as long as possible, but I archive and print in
8-bit (except for the most valuable images, which I archive in 16-bit TIFF,
but I still convert to 8-bit for printing).