Digital BW, The Print

I think it is preferable to make one curve adjustment if at all 
possible.  Each levels adjustment equals one curve adjustment no 
matter what you do.

mark

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Stephen Kobrin" 
<skobrin@h...> wrote:
> 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
> > *