Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, 
"johngeyles" <jge@c...> wrote:
> 
> > 8 bit  to 16 bit conversion is so straightforward it's hard to
> > imagine why it would be better to do it before sending data to
> > OPM.   
> 
> I am purely speculating here ... but one can imagine an 
8bit->16bit
> conversion that is not quite as straightforward and might create
> a better image.  The idea would be to make the hi-byte of the 
16bit
> value equal to the 8bit value, and then put a random value into
> the low-byte.   This has the effect of reducing "mock bands" at 
the
> transitions between the 256 values; it is frequently used in 
> computer image generation systems.  However, I'd be very 
surprised
> if Photoshop does this when you convert "mode" from 8bit to 
16bit,
> in which case this wouldn't explain the supposed improvement 
from
> OPM when you give it 16bit images,
> 
> John

Yes, adding noise to the bottom byte could be done.  But
Photoshop doesn't . It actually takes the 8bit number and
multiplies by 257 -- puts same value in each half of the
16bit value, that way 0 ==> 0 and 255 ==> 65535.

Roy