Digital BW, The Print

* -----Original Message-----
* From: Tom Baker [mailto:tbaker1328@sbcglobal.net] 
* Sent: Friday, November 28, 2003 9:46 PM
* To: DigitalBlackandWhiteThePrint@yahoogroups.com
* Subject: Re: [Digital BW] 16 bit printing
* 
* 
* Paul  -
*  
* What would be the result if you had started with a 16bit 
* image, done all of your work, including the curves 
* application, then converted to 8bit just before printing?  
* Similarly, what happens if you apply the curve before 
* converting to 16 bit in your most recent scenario?  The 
* reason I ask is that I'm still wondering if, when, and how it 
* makes a difference if you print an 8 or 16bit gray file.  
* I've printed some 8bit files that look just fine.  But, that 
* seems illogical.
*  
Tom,

I'll put my 2 cents in here if you don't mind. For the most part you can
make great prints working and printing in 8-bit mode. If you couldn't then
we would not have gotten as far with this as we have.

However, it is desirable to do everything in a higher bit mode. As you
adjust an image you can start to chop up the data in 8-bit to the extent
that not all of the 256 shades of gray are used and your histogram appears
"combed" and/or fuzzy. You can actually have quite a lot of this and still
get a good print but you frequently wind up with problems of posterization
and tonal flat spots in areas like skin or skies. In 16-bit with 65,536
shades of gray you can lose thousands of shades and it will never be visible
in the print.

Many people have always worked their prints from beginning to end in 16-bit
mode but for the majority the lack of layers and other tools in 16-bit mode
was not acceptable and we dropped down to 8-bit after making some initial
adjustments.

The great thing about Photoshop CS is that you now have all of the tools and
layers available in 16-bit that you had in 8-bit. The bad news is that the
working file sizes get really out of hand as you start adding layers in
16-bit mode. However, the good news is that you can save an initial 16-bit
version of your file and then an 8-bit version. Work out all of your layers
and adjustments in the 8-bit file. When you are done put all the layers in a
layer folder, open up the 16-bit version of the image you saved, drag the
layer folder from the 8-bit to the 16-bit image and presto you have a 16-bit
file that is identical to what you would have had if you had done all the
work in 16-bit. Very cool!

In PS7 and earlier if you did all of your adjustments in 16-bit and then
converted to 8-bit before applying the RGB separation curves you would
"damage" the image data when the curves were applied. Might or might not
effect image quality depending upon the image. Same thing if you applied the
curves to an 8-bit file prior to converting to 16-bit. Once the damage has
been done in 8-bit converting to 16-bit does not help.

If you were not using RGB separation curves, then converting from 16-bit to
8-bit prior to printing would not cause you any problems. However, there is
no reason to convert a 16-bit file to 8-bit prior to applying the curve or
prior to printing. Just print directly from 16-bit.

Martin Wesley
http://www.carolyn.cc/Guests/MartinWesley/pages/MW_01.html
http://www.borderless-photos.de/guests.html