Digital BW, The Print

* -----Original Message-----
* From: Stephen Kobrin [mailto:skobrin@hotmail.com] 
* Sent: Tuesday, September 30, 2003 5:54 AM
* To: DigitalBlackandWhiteThePrint@yahoogroups.com
* Subject: [Digital BW] Re: New Photoshop CS -- aka Photoshop 8
* 
* 
* Martin,
* 
* Can't you set the black and white points in curves just as well 
* (along the x axis)?  Is there a difference between using levels to do 
* this and constraining the x axis in curves?  I thought a discussion 
* earlier this summer established that levels tends to degrade the 
* image much more than a curve adjustment.
* 
Steve,

Yes you can but I find it easier to do it in Levels since I set the two
points using the sliders based upon the information displayed by the
histogram. What I don't use in Levels anymore and what I think causes people
problems is the gamma adjustment. Changing gamma applies a curve to the
image but you can't see the shape of the curve like you can using Curves.

So I like to do it as a two step operation of setting end points in Levels
with Silverfast and shape contrast with Curves in PS. Like just about
everything in digital image editing there are multiple paths to the same
destination.

Martin
* 
* --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Martin Wesley" 
* <mwesley250@e...> wrote:
* > * -----Original Message-----
* > * From: Mark Hahn [mailto:markhahn2000@y...]
* > * Sent: Monday, September 29, 2003 8:58 PM
* > * To: DigitalBlackandWhiteThePrint@yahoogroups.com
* > * Subject: Re: [Digital BW] New Photoshop CS -- aka Photoshop 8
* > * 
* > * 
* > * Not really... at least if you agree that the human eye can't 
* > * distinguish between more than 16 million colors.  The real 
* problem 
* > * with 8 bits per channel is with the fixed precision math that is
* > * performed for each adjustment... you get rounding errors which 
* become 
* > * cumulative and destructive.  This is much reduced when
* calculations 
* > * are done in 16 bit mode.
* > *
* > * mark
* > * 
* > * PS  I am working on an image editing package that works at a 
* fixed 64 
* > * bit depth per channel and maintains butter smooth tones through
* out 
* > * any number of adjustments... but it runs way slower than
* PhotoShop;)
* > *
* > Mark,
* > 
* > I think that 256 shades of gray are probably more than adequate for
* B&W
* > printing but as you note, adjusting an 8-bit file causes that
* number to
* > drop. Fortunately we can actually lose quite a bit and still come
* up with a
* > good print. I suspect that as few as 100 shades of gray may be
* acceptable in
* > some images but it is very easy to fall below an acceptable
* threshold if you
* > are not careful.
* > 
* > With the 65,536 shades of gray available in a 16-bit file the
* chances of
* > having it visually degrade during Photoshop adjustments is greatly
* reduced
* > to say the least. Although I imagine if you try hard enough you
* will still
* > get things out of whack!
* > 
* > At 64 bit or 18,446,744,073,709,551,616 shades of gray you are
* probably way
* > beyond what is needed. In all honesty I wonder if we couldn't do
* just fine
* > with say 12-bit or 4096 shades of gray. In any case you don't need
* more that
* > your scanner or digital camera can output and this has been in the
* 10 to
* > 14-bit range.
* > 
* > It is interesting to note that even when you scan 10 to 14-bit data
* to a
* > 16-bit file you can lose image data if you do not spread that data
* over the
* > full 16-bit range before you start applying gamma or curve
* adjustments. In
* > other words you need to set your black and white points in levels
* first and
* > seperately before any other adjustments.
* > 
* > Martin Wesley 
* > http://www.carolyn.cc/Guests/MartinWesley/pages/MW_01.html
* > http://www.borderless-photos.de/guests.html
*