Digital BW, The Print

Paul,

everything you say regarding the effect of the high bits on the actual image 
are undisputable, and certainly something that all bw printmakers should be 
aware of  (much more so than color where you can hide behind 3x or 4x the 
digital information). 

The thing with OPM is that it was built  on (or came from) a 16bit engine,  with 
8bit support only added very recently. Any decent driver needs to work in 16 
bits internally anyway to avoid quantization errors. However, there may be 
weaknesses in the 8-to16 bit internal conversion with OPM, that make it a 
"safer bet" to give it a 16 bit file.  The latter bypasses an extra step in the driver 
and takes out some variables (that only Joe would know to tell you about).

I personally haven't seen a good reason to bumb up the file to 16 bits or to 
even hit 720 dpi unless the initial res is too close to 360 or the file has a lot of 
sharp diagonals etc. But if I ran into any questionable output, those would be 
the first things I would try.

In short, I just wanted to point out that the issue of 8 vs 16bits in this scase is 
solely for the purpose of helping out the driver and has nothing to do with our 
usual concerns of preserving the gray steps in a monochrome image file.

Antonis







--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul Roark" 
<paul.roark@v...> wrote:
> 
> >... at Bowhaus (the guy behind OPM/IJC) he
> >would work on the photo in 8-bit, and only convert it back
> >into 16-bit for the actual printing. ...
> 
> This must be the reflection of a strange driver/RIP.  It makes no sense to
> me otherwise.
> 
> Once you convert to 8 bit you've lost the additional information/grayscale
> steps 16 bit can hold.  Conversion back to 16 bits from 8 bits does not
> restore those lost steps; it does not add information.  You have the same
> number of grayscale steps you had in the 8 bit image, but with a file that
> is twice as big.  Why would one do this?
> 
> I agree that 8 bits is all that is needed for a fine B&W print, but it is in
> the manipulation stage where there is a major loss of information.  When 
you
> apply curves, etc., you lose grayscale steps.  The purpose for keeping the
> file in 16 bit as long as possible is usually to have enough extra
> steps/information so that when you're done you have at least close to the
> 256 gray levels that 8 bits can hold.
> 
> If you drop much below 256 levels, the quality of the image may suffer.
> Take a look at a print of the 100-step test file.  You can clearly see those
> steps.  That means that 100 levels is not sufficient for a very fine grain,
> clear sky.  (Grain will help to mask this problem if it surfaces -- but that
> is not a very attractive remedy.)
> 
> Paul
> http://www.PaulRoark.com