Digital BW, The Print

Hi Allessandro,

Well on my images the noise in the shadows on the monitor is very
obvious when I scan a slide in 8 bits. If you make a large tone
adjustment in an 8 bit scan and then scan the same slide in 16 bits and
make the same adjustment, its obivous on my monitor that the 8 bit scan
is inferior. I don't have to make a print to prove it. Its almost always
that noise shows up in the shadows. Also splotches, or mottle. This
doesn't happen in 16 bit.

 I realize this is image dependent, and wouldn't show up in all images.
It doesn't show up in ALL my images, and never in digital camera images.
I usually shoot the digital camera images in raw, make any curve
adjustments and then save it in 8 bits.  There isn't a posterization
problem at all with my Canon D30. In fact, I don't think I've ever seen
posterization in any image taken with the camera. Shadow detail with a
digital camera seems a lot better than with film, so It might not even
need the 16 bit raw image to begin with, but I do it anyway, just to be safe.

It's much worse in scanning a black and white negative, and if I'm going
to make a large tonal adjustment, I MUST scan the negative in 16 bit.  

If you just scan and print and don't make any curve or level adjustments
at all, then it isn't nearly as bad, and in small prints, probably
wouldn't even show up.  A lot of images probably don't need a lot of
tonal adjustments. But I have this one particular client who insists on
using slow, contrasty films like velvia. And you have to make a real
effort to get acceptable (Not great, just acceptable) shadow detail,
requiring a very large curve adjustment. I just couldn't do it in 8 bit. 

I hope this discussion will result in people actually trying this for
themselves, and see the results on their own screens. If nobody can see
the difference, on their monitors, I must be doing something very
wrong!! I could have some setting wrong and that could be the cause. 

> I was rigorous, and I saw no difference *on screen*.

Maybe your scans are so good that you don't have the problem. I would
imagine a drum scan wouldn't have nearly the problems that ordinary
desktop filmscanners have.

Just out of curiosity,
> what do you think is the reason behind posterization showing up only on the
> print? 

For me, I can see the difference on the monitor. It looks like mottled,
spotchy patches.

Jerry