Re: losing colour in Acrobat

[Michael Richards <michaelr@xxxxxxxxxxxxxxxx>]

I am getting a little confused here, folks, and this topic is suddenly
becoming extremely profound!

Debbi, may I ask you to clarify your reply a little?

Specifically the phrase "ppd fixes to  use cmyk". From the  little I know of
the pdf format internals it's my understanding that:

         1) Internally pdf can have objects in a single file with different
colour
             models, i.e. rgb, cmyk, cie et al (but NOT indexed colour such as
             in all GIFs and most TIFFs)

         2) That (and from here on I will assume eps graphics only to sidestep
             other issues!) if the eps COLOUR SCAN is rgb, the rgb colours
pass
             straight through Distiller, HOWEVER

          3) Acrobat Reader/Exchange DOES apply its own transfer curve to
display
             these colours, so they might look a little different from those
             you were expecting.

          4) If the eps COLOUR SCAN is cmyk, distiller turns this into rgb
using
             (roughly speaking!) the notorious Photoshop CMYK seperation
formula
             but in reverse, resulting in wishy washy colours without strong
reds,
             magenta-muddied blues, etc.

          5) If you set distiller to pass through cmyk AS cmyk, the display on
             screen in Reader/Exchange is very colour saturated. That's (I
             beleive because the coloour-draining algorythm of 4) has been
side
             stepped.

I say COLOUR SCANS as things are a little different for Duotones and
Illustrator vector drawings. This is (in simplistic terms!!!) because both
these formats have internal, explicit info in the eps file telling the RIP or
whatever the rgb representation of the spot colour(s). Another topic. Let's
not muddy the waters further!

Now, (deep breath) Debbi, do you mean cmyk in, rgb out? Or cmyk in, cmyk out?

BTW, a good way to get a decent colour sep on Photoshop is to use the Soft
Light/Hard Light trick. This means:

1) SCAN in RGB (D'oh! That's how you do it anyway!)

2) Change the mode to CMYK.

3) Then, in the layers pallette, double click on the "Background Layer" and
"un-flatten" the image by renaming the layer in the resulting dialogue as
"layer 1" or in fact anything other than "Layer 0".

4) Make a new layer on top of the old. Its mode is either "Soft Light" or
"Hard Light" (if you want REALLY STRONG COLOURS!!!!!!)

5) Now, make sure the old layer is active and copy its entire contents to the
clip board.

6) Make the new layer ("Layer 2" most likely) active, and paste.

7) Wow! what a great seperation! If it's a bit extreme, reduce layer 2's
opacity to 50% or whater.

MAGIC!



Debbi Leipold wrote:

> Dov et all,
>
> I disagree. I have found that PDF will not display process color correctly
> and that is necessary even with all of the "right driver" and ppd fixes to
> use cmyk.  i think Shlomo agrees with this as he and I discussed it at the
> conference.  Maybe it is a bug but it is definitely an accomodation most of
> us have had to make.
>
> Photoshop generated eps with two colors must be duotone to separate and
> display correctly in pdf.
>
> Any other screen capture type illustration in tiff must be cmyk to work.
>
> These are the rules I have found to be fulproof when converting color to
> PDF.
>
> Debbi
>
>

<snip of earlier threads>

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