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Author Topic: Drafting a colour management instruction sheet for inexperienced users  (Read 3426 times)

crlMIDI

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Hi,

There's a lot of information available on colour theory and management, but I think it would be useful to have a set of very specific instructions for non-expert end users, to be adapted to each hardware & software combination.

The printshop in town is very helpful but it's good to know in advance what to ask for, and to get things right first time.
The subject has become important to us because we're working at the local book club on an illustrated children's poetry book. The pictures are in really bright colours and we want to do them justice.

I'd be grateful for comments on my draft instructions, which include some questions I haven't been able to answer, particularly those relating to possible misunderstandings with Scribus settings.

Present setup
Windows 8.1 professional, with Scribus 1.4.5, Photoshop Elements 11 and sometimes Gimp. The Epson Pefection 4490 scanner uses Epson Scan Version 24F (there's some confusion on the web about colour management with this excellent series of scanners). Everything is in French, though Scribus was set to English to check the terminology.

Scanning instructions
Set Epson Scan to professional mode and go into the Colour tab of Configuration. Select Colour Controls and check Apply Automatic Exposure, with gamma 1.8. Scan your pictures to tiff, typically at 600dpi.

Photoshop Properties will indicate that the tif files are tagged with ICC profile EPSON Standard RGB - Gamma 1.8; this is retained if subsequently you make psd and png files.  The corresponding profile file is ewrgb18.icm, in c:\Windows\System32\spool\drivers\color.

Photoshop can convert this profile to sRGB or Adobe RGB but there may be no advantage doing that. You can also set Epson Scan to different source and target ICM profiles, though the automatic exposure option seems to work OK for me. It is not clear from web searches that automatic exposure mode does in fact tag tif files with a genuine ICC profile.

Question: some people propose that scanned images don't need a profile; should we use a profile if the scanner software tags one onto the file without asking?

Clipping images
If the pictures are drawings, on white paper for example, and they can be clipped, you may want to make their background indistinguishable from the book page, so that no picture framing is needed.
A simple way is to use PS or Gimp to make a pure white clipping mask (RGB #ffffff), covering at least the edges of the image. You then collapse the layers into a simple tif file.
Question: to be able to do this, we need to be assured that, with colour management on, RGB white always translates to "zero ink" in the CMYK rendering.

The other way to clip is to make the clipped parts transparent.
Question:  is it better to use tif or png with Scribus (doubts have been expressed about tif transparency working correctly)? Also, we need to be sure which pdf formats will work reliably at the printers.

Scribus settings
In Scribus Preferences, General, make sure the ICC profiles path is the one given above (in my case c:\Windows\System32\spool\drivers\color).

In Preferences or Document Setup, activate Color Management. Set System Profiles, RGB Images, to EPSON Standard RGB - Gamma 1.8 or whatever profile your scanned images are tagged with.

Question: I'm not clear how this interacts with the individual ICC profiles of images in the Scribus document, which can be changed via F2 and seem to make the global setting redundant.

Set the printer profile to the one supplied or indicated by your printshop. You don't need to change the other System Profiles. Leave the Rendering Intent for images at Perceptual (are there exceptions worth bothering about for artistic work?). Leave Use Blackpoint Compensation checked.

PDF export
When your document is done, open Export to pdf. On the General tab, set File Options, Compatibility, to PDF/X-1a or PDF/X-3a depending on printshop requirements. It doesn't seem possible to give unambiguous advice on this choice without specific  information from the printshop.

The Color tab will have Output Intended For Printer greyed out.

On the Pre-Press tag, you can change the Output Profile under PDF/X Output Intent.
Question: we need to know whether selecting a profile here overrides the corresponding setting in Preferences or Document Setup.

A bit off-topic: don't forget to embed your fonts; it may be preferable to outline them all unless (unlikely for an amateur) the pdf might be modified pre-press. Outlining should ensure no surprises regarding unexpected glyphs.


a.l.e

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hi crIMIDI

under what license are your instructions?

ciao
a.l.e

crlMIDI

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hi crIMIDI

under what license are your instructions?

ciao
a.l.e
Hi a.l.e

I don't really understand your question - I wrote the text firstly as a way of formulating a set of questions about the way Scribus fits in with a workflow that can be followed by authors I know who want to prepare their work ready for printing.

If the approach turns out to be of any use it will end up on our new and presently fairly empty website (www.livredorge.org), and/or anywhere else you like. There seems to be a gap to be filled: advice from online publishers serving private individuals tends to be too simple and Word-oriented. It ignores the fact that you can obtain fully professional results with open source. Printshops where you can have a conversation with real people will quite obviously be using only expensive commercial software, so providing step-by-step instructions for making the good pdf's with Gimp/LO/LaTeX/Scribus (etc) is our job.

a.l.e

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hi crIMIDI

because if i read, comment, and enhance your instruction i want to know under which conditions i might use and publish them myself.

if you set them under cc-by-sa i'm more than happy to have a look at them!

i'm leaving today for a trip to vienna... so it might not during the next few days...

have a nice day
a.l.e

p.s.: i'm writing a ticket to have a notice in the footer of the forums that the posts are "cc-by-sa".
except the author explicitly states something else.
is anybody against it?

utnik

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hi crlMIDI

…should we use a profile if the scanner software tags one onto the file without asking?

for color sensitive products you always need color profiles!
the best would be a hardware calibrated working place, including cameras, scanners, printers, monitors and a standardized working light – but no amateur will have this. (i work on a system 'calibrated by eyeball' – but with all the profiles…)
if your scanner comes with a standard profile, use it as long as you don't make your own (with the actual condition of your unit…)

Quote
to be able to do this, we need to be assured that, with colour management on, RGB white always translates to "zero ink" in the CMYK rendering.

RGB #ffffff should always become CMYK 0, 0, 0, 0.

Quote
is it better to use tif or png with Scribus (doubts have been expressed about tif transparency working correctly)? Also, we need to be sure which pdf formats will work reliably at the printers.

as long as we're talking about clipping (full transparency and full opacity) it doesn't really matter. and with native transparencies (semi transparent parts) you need a .pdf version higher than 1.4 (.pdf/x-1a and .pdf/x-3 are based on 1.3. they don't support transparency.)

for the .pdf version you should ask your printshop.

Quote
I'm not clear how this interacts with the individual ICC profiles of images in the Scribus document…

this is a standard for images without any embedded profile. as long as you keep the embedded ones intact, you better use sRGB or eciRGB as a standard.

Quote
…Rendering Intent for images at Perceptual (are there exceptions worth bothering about for artistic work?)

usually not. but if a part of an image should flow seamlessly into a colored area, the two of them will need the same rendering intent. (by default images are set to 'perceptual' and graphics to 'relative colorimetric'…)

Quote
…you can change the Output Profile under PDF/X Output Intent.
Question: we need to know whether selecting a profile here overrides the corresponding setting in Preferences or Document Setup.

yes, it does.

utnik

Nermander

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One major problem is that there really is no good "easy" way to color management.

Without correct profiles turning on color management may give you worse results than keeping it turned off.

crlMIDI

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One major problem is that there really is no good "easy" way to color management.

Without correct profiles turning on color management may give you worse results than keeping it turned off.

A couple of years ago I did some posters with photos and text for an exhibition without bothering about colour management. The photos were disappointingly dull, so for our picture book I thought I'd try and do it properly.

Thanks to Utnik's replies above I should be able to do this, as they make clear which Scribus settings override others. At least I'll be able to discuss the subject with the printshop without appearing completely stupid.

I forgot to ask about just one point: if for some reason you change the image profile in the Properties of a particular image frame, does Scribus convert from the old profile, or assign the new one as though no profile existed before?

Nermander

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As I tried to get through: color management depends on correct profiles, it's not a matter of "settings" but rather to measure the properties of the printer and your screen.

utnik

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hi crlMIDI

if for some reason you change the image profile in the Properties of a particular image frame, does Scribus convert from the old profile, or assign the new one as though no profile existed before?

i didn't test it, but i assume scribus would take the changed profile as the source for its cm. (i always import profiled images…)

As I tried to get through: color management depends on correct profiles, it's not a matter of "settings" but rather to measure the properties of the printer and your screen.

i calibrate my screen 'by eyeball' with a professionally printed cm-testform and the appropriate .pdf file. my working place is far from any window, still 'contaminated' by some daylight – not optimal, but ok.
for the printer i use the profiles from the printshop. (my own printer is too weak to be included in a cm workflow…)

utnik