Grays & Color percentages not matching on PDFs

Tue Jan 29 14:19:17 CST 2008

Brad Crocker wrote:
> I thought Photoshop was embedding the color profile but now I'm not 
> sure, all artwork is worked on and saved as CMYK, I have not used any of 
> the Creator color matching settings (I was unaware of that aspect of the 
> program!) My Photoshop color settings are as follow:
> 
> Settings: Custom
> RGB: rRGB IEC61966-2.1
> CMYK: SWOP (Newsprint), 30%, GCR, Maximum
> Gray: Dot Gain 30%
> Spot: Dot Gain 20%
> Color Management Policies
> RGB: Preserve EMbedded Profiles
> CMYK: Off
> Gray: Off
> 
> 
> This is mostly Greek to me. (I understand what the color spaces are and 
> their uses, but the individual settings don't mean much to me. Two areas 
> in Photoshop that concern me - the dot gains & the color management 
> policies. (Should CMYK be set to conserve profile or convert to working 
> CMYK?) If I get these set correctly, how should I set up the Creator 
> color mathcing to best reflect the proper color.

Hi Brad,

Let's see if I can provide some pointers without confusing anyone..

First of all, if you are using any RGB images anywhere, be sure to 
change sRGB to Adobe 1998 RGB in PhotoShop.  sRGB clips a LOT of color 
because it represents the maximum color an older PC monitor can handle.

For how you should handle embedded profiles: I support a design group of 
18 MACs, and have it set to 'Convert to Working ____' for all color 
spaces.  I have also turned off the 'Ask when Opening/Pasting' options.

If an outside image has an embedded profile, then PhotoShop will have a 
clue about how the user was looking at the image on their PC/MAC 
(leaving color calibration out of it) and how their PhotoShop settings 
were configured.  Your PhotoShop will then automatically do the 
conversion to the settings you need for your press.

If an outside image withOUT an embedded profile is brought into 
PhotoShop, then it'll be assigned to your working settings, i.e. your 
RGB setting and your Custom 30% dot gain CMYK setting.  If it is RGB and 
  you then convert it to CMYK, then it'll convert to your colors just 
fine.  However if it is CMYK, it is likely that the outside user did NOT 
have your press's CMYK configuration loaded - how are they supposed to 
know?  It is likely that they converted the image to CMYK using 
PhotoShop defaults - most likely 'US Web Coated (SWOP) v2'.  (Lots of 
'likelys' here aren't there :)  You'll probably notice that the image is 
darker than it could be, since US SWOP is 20% dot gain and you are 
looking at it through the eyes of 30% dot gain.  You can adjust using 
levels or curves, but an easier method is to create an action that does 
this:

1) Apply the Color Profile 'US Web Coated (SWOP) v2'
2) Convert to Profile - 'Working CMYK' with Adobe ACE engine, 
Perceptual/Relative Colorimetric, Use Black Point Compensation, and Use 
Dither.

The first step assigns a profile to the image so PhotoShop can do the 
onscreen conversion for you, making it look lighter.  The second step 
converts the CMYK values from US SWOP to 30% so that when you save it 
your numbers will be for your press.  If you like what you have, save. 
If not, Undo twice.

The next question - to save your images with an embedded profile or not?

If you will be using the images internally only, and with one press 
only, then saving with an embedded profile (and increasing the file 
size) is not strictly necessary.

However if in the future you use another press, or an ad is collected to 
send elsewhere, or even just to be explicit with your other software 
programs - save it with the embedded profile.  A CMYK profile is only a 
meg or so if I remember correctly.

I recommend also that you take that Custom PhotoShop CMYK setting and 
name it and Save it, creating an ICC profile on your Machine.  In 
PhotoShop, just click on the CMYK setting as if you were going to select 
Custom and change it, but instead Save CMYK.  Then distribute this ICC 
profile to all the other Machines.  I have ours named as 'Day Newspaper 
CMYK - 2005-03'.  If we ever need to change the profile, I'll resave it 
with a new date and kick off a PhotoShop action to load all and convert 
to the new name.

Finally, Creator preferences.  I strongly recommend that you use them, 
to get an onscreen feel for the colors you are using.

I have Creator's Color Matching for RGB graphics without an embedded 
profile set to 'Ask User' so they'll know they are placing RGB - and to 
go back and resave as CMYK for the ad.  For CMYK, I have it set to 
'Document CMYK Input Profile' - whatever is in the document's settings 
will be used, in case you build an ad for more than one press.

In Document Settings, I have Color Matching turned on.  For RGB, I have 
it set to 'Adobe RGB (1998)' and Perceptual.  For CMYK I have it set to 
the CMYK ICC profile I saved earlier for our press and Perceptual.  In 
this way your colors will be adjusted onscreen for your press.  I have 
the Output profile set to None so color percentages are not adjusted on 
the way out of Creator.

I welcome any feedback others have on these suggestions!

thanks,
-- 

chris denesha
Advertising & Telephone Systems Support, IT
The Day Publishing Company
(860)701-4485; OR (800)542-3354, X4485
c.denesha at theday dot com - Work email
chris-list at denesha dot org - List email