Digital BW, The Print

What I actually do is to use levels to determine the black and white 
points using the historgram and then actually set them in curves.  I 
gather from your post that this is not necessary as long as I do not 
fool with the gamma adjustment in levels.  Thanks Martin.

Steve

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Martin Wesley" 
<mwesley250@e...> wrote:
> 
> 
> * -----Original Message-----
> * From: Stephen Kobrin [mailto:skobrin@h...] 
> * 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
> *