Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "luisvcool" <lvictoria@t...> 
wrote:
> Ok.  If i scan an image at 8 bits and before I print in on OPM I convert it to 16 
> bits in PS7 and save the file,  will the resulting 16 bit image look better than if I had 
> saved it at 8 bits and then printed it?
> 
> I'm confused.
> 


A couple of months ago I discovered that OPM prints from 8-Bit files at resolutions 
under about 450 dpi displayed stair stepped diagonals - at least when examined with 
a loupe. So, I did a series of prints to examine the 8-Bit vs 16-Bit treatment with 
OPM. There was no question that feeding OPM with a 16-Bit file was better than with 
an 8-Bit file. The effect was about the same as resampling an 8-Bit file up by a factor 
of two. An 8-Bit file at 720 dpi produced about the same results as a 16-Bit file at 
360 dpi.

I don't know why this occurs, but I satisfied myself with the rationale that OPM 
requires a 16-Bit file, and does an internal conversion to 16-Bit when fed files that 
are at 8-Bit. Apparently the OPM conversion routine has a problem. So that problem 
can be avoided by always feeding OPM with 16-Bit files. Within PS7 there is no 
apparent effect of a simple 8- to 16-Bit conversion so it is much better approach 
than resampling to solve the problem.

Doug Nielsen