Digital BW, The Print

Maybe obvious to most, but for new users be sure that the "use cache 
for histograms" is not checked in general preferences. If this box is 
checked, PS will display the histogram faster, but the info is based 
on a representative sampling of pixels instead of all the pixels. 
Access preferences under "edit" on the PC and select "Memory and 
Image Cache", and unchek the box. Also set to levels of cache and 
memory allotment here. You can also display a histogram using all 
image pixels by pressing the shift key while choosing 
Image>Histogram. If you've reset your preferences lately, may want to 
check it out. Timely info from Carla Rose in the latest issue of 
Photoshop User.

Barry Gilliand

--- In DigitalBlackandWhiteThePrint@y..., "Michael Kravit" 
<michael.kravit@w...> wrote:
> Barry,
> 
> If you create a gradient in PS and then posterize it creating 21 
distict
> patched you get a histogram with 21 vertical lines. This is because 
the
> image is no longer a gradient.
> 
> Now, if you create a second gradient without posterizing it so that 
it is as
> smooth as Photoshop can make it you will have a histogram that is 
sold with
> a gradual arc that is high at the ends and slopes down a bit in the 
center.
> 
> There may be roughness at the top along the curve, but you do not 
have deep
> fingers indicating that data is missing.
> 
> Mike
> 
> 
> ----- Original Message -----
> From: "flyfishingusa2002" <tflyfish@c...>
> To: <DigitalBlackandWhiteThePrint@y...>
> Sent: Sunday, March 24, 2002 11:08 AM
> Subject: [Digital BW] PhotoShop Histograms leading us astray?
> 
> 
> > I have been following all the threads regarding "Combing" 
and "Step-
> > Wedges" with great interest. I have been looking at there 
Histograms
> > in Photoshop and trying to figure out what it was telling me. I 
have
> > been seeing a lot of "stray" information in the Histograms that
> > confused me, so I decided to try the following:-
> >
> > 1  I did a selection of just the wedge part of the published
> > standard Step wedge by Jon Cone and MIS
> >
> > 2  I, via PhotoShop 6, drew a simple rectangle filled with a
> > graduation from 0% - 100% grey.
> >
> > Neither of the above gave me a "Clean" Histogram. I fully expected
> > #2 to do so. I see lots of little comb teeth and a variation in 
the
> > histogram height when I thought it should be constant.
> >
> > Could it be that the "Combing" is something that Photoshop is
> > introducing and does not really appear on our finished print?
> >
> > I have also noticed that on the step wedge that those little white
> > dividing lines do not appear between all the steps on some
> > magnifications and not on others.
> >
> > I am no PhotoShop expert, but the above seems a little odd, maybe 
we
> > are all being lead astray by PhotoShop?
> >
> > Barry
> >
> >
> >
> > Please visit the Group Homepage to check the Files, Bookmarks, 
Polls and
> other resources as they are often being updated. The page is at:
> >
> > http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> >
> > Please follow these basic guidelines:
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> >