[Scribus] The colors from the print are not expected.

[Craig Ringer]

> Adolfo Jos? S?ez Folgado wrote:
> 
>> I must bear in mind that different inks and papers give different
>> results, but how and when?
> 
> "it varies". It's rather hard to predict.

Just to clarify, in the following I meant "print shop" where I said 
"printer". It's common usage but can easily get confusing. I had someone 
point out (correctly) that it's particularly confusing here, so I 
thought I'd clarify just in case it's useful.

I've applied clarifications in [ brackets ] below, for that issue and 
others.

> The only way you'll find out for sure is to arrange "real" dummy proofs 
> with your [print shop], where they actually make the plates, run up the 
> press, etc. This is, unsurprisingly, expensive, though not as costly as 
> having to re-print the entire run. It is really the only way, even now, 
> to be truly sure that your job will have the colour you wanted it to.
> 
> If you can't get dummies, find out if your [print shop] offers any sort of 
> soft-proofing. Some [print shop] can do quite reasonable simulations off 
> high end laser [print shop], where they run the job through the same RIP 
> they run the press off. Others might offer on-screen proofing in an 
> environment with controlled lighting and a very high end monitor. As far 
> as I know neither of these options can do a complete job of accounting 
> for different inks, media, etc, unless the press has been measured with 
> that particular combination. If the press has been measured with the 
> media you'll be using, etc, then the results should be very similar to 
> what'll print, and with a good soft proofing setup should be pretty 
> trustworthy.
 >
> If your [print shop] can't offer any sort of soft proof for you, you can try 
> doing some yourself. You must have a good ICC profile for your press or 
> you are wasting your time with this. Even with a good press profile I 
> would not rely on the results personally. This is rarely as easy as 
> setting a proof mode on a [laser/inkjet] printer. Maybe there are 
 > [laser/inkjet] printers out there
> that do a decent job of simulating a press out of the box - but I've not 
> seen one yet. Someone PLEASE yell at me if they've had more success, 
> since I'd love to be shown to be wrong. Anyway, as far as I know to get 
> results you can rely on you'd probably have to do some proper 
> calibration on your [laser/inkjet] printer - requiring somewhat
 > expensive hardware to
> measure its output.* Assuming you *do* have an accurate profile for your 
> [laser/inkjet] printer and for your press it's possible to simulate the
 > behaviour of the press on the [laser/inkjet] printer (with some
 > limitations if the [laser/inkjet] printer's gamut
> is more limited than the press's). The `tifficc' utility can actually do 
> this to an extent, and there are lots of commercial soft proofing 
> software options too.
> 
> Of course, if your press profile is good, your display profile is good, 
> and your software is doing its job, in theory your on screen results 
> should look similar to what'll print anyway. This will only be true if 
> your software is set up for colour management and you have told it to 
> simulate the printer on the screen.
> 
> Since right now it seems that you are not actually using a profile that 
> is specific to your press, that is probably the first thing you should 
> fix. Get an ICC profile from your [print shop] that describes their 
> particular press (and preferably media). They might tell you that their 
> RIP expects Euroscale Coated (or uncoated, if you're printing uncoated) 
> input, in which case you're OK with a generic profile since their RIP 
> will compensate. You really do need to check that, though, since some 
> [print shops] expect you to use a generic profile and compensate, others want 
> you to use their profile, and others again just won't know what you're 
> on about with all this "icc colour" stuff.
> 
>> I can not accept with a red selenium lamp leaves printed in the
>> catalog as dark orange
> 
> If I'm not mistaken, you will have used a very intense, saturated red. 
> What kind of press are you going to be printing on? Many print 
> configurations won't handle some really intense reds and some other 
> colours. The use of such colours is called using "out-of-gamut" colours 
> - colours that the press cannot reproduce. Since your screen can 
> probably handle them just fine, they look OK on screen but won't print 
> properly.
> 
> The problem you describe would be consistent with colour clipping / 
> shifting caused by the use of an out-of-gamut colour.
> 
> Have you used the "press simulation" mode with gamut warning enabled to 
> check if the colour management engine thinks the problem colours are
 > out-of-gamut for your press? It's possible to check for such problem
 > colours (within limits) and warn about them. If you're NOT using press
> simulation mode then you can use colours on screen that your press won't
 > be able to handle and you won't have any idea you've done it.
> 
> Scribus can do on-screen press simulation and gamut warning. See the 
> colour management preferences. Photoshop can also do it for particular 
> images, which is useful when you're working on adjusting an image to 
> print better. I think Krita 2 (coming in KDE 4) will do this too - hooray!
> 
> If the colour is out of gamut for your press, you have a couple of options:
> 
> - Make the whole image paler / duller / less saturated to bring the
 > out-of-gamut colours back into the press's gamut. Playing around
> with the  image in Photoshop  while press simulation and gamut
 > warning mode is on is quite handy if you're trying to do this.
> This is probably your best option, and it's the only one I know of
 > that won't cost you a bunch of extra money
> (except ignoring the problem). At the newspaper I work for we either 
> tweak the image to print OK or we find a more suitable image.
> 
> - Spend more on a more expensive print run with better stock, fancier 
> presses, etc that can handle the difficult colour. For example, if 
> you're using cheap uncoated printing with coarse stock, you might find 
> that a coated press with better stock gets you an improved gamut that 
> can handle the difficult colour. But is it worth the extra cost?
 >
> - If you're trying to match a very specific colour sometimes your 
> printer can add it as an extra ink, you might print with (eg) CMYK + Red 
> . This is called spot colour printing. It won't help you if you're 
> trying to improve colour in photos etc, and is mostly useful for logos.
> 
> - There are very special print processes that use more than four colours 
> for all colours - like HexaChrome for example. They're generally really 
> rather expensive but I mention them for completeness. If you used a 
> printer that used one of these processes you'd probably send them tagged 
> RGB PDF, not CMYK.
> 
>> or a single PDF file that is so different from
>> one machine to another, whether it is also not the fault of my work or
>> the printer.
> 
> A pdf almost always obviously appear differently on different computers 
> with different screens, OS versions, etc. This is because different 
> screens, video cards, etc display the "same" colour totally differently. 
> The computer cannot see the colour on the screen so it has no way to 
> compensate.
> 
> The only time there should be any exception to this is when the computer 
> you are viewing the PDF on has a properly calibrated display and you've 
> enabled colour management in Acrobat. To calibrate a display you really 
> must have a hardware calibration device. By eye calibration really 
> doesn't do the job. If you have two computers with properly calibrated 
> displays the same PDF should look very similar when viewed on both, so 
> long as the colour settings in Acrobat are the same.
> 
> If you're trying to use Acrobat to preview the PDF, make sure to tell 
> Acrobat to use the ICC profile for your press as its CMYK profile. 
> Otherwise you'll be getting wrong results since Acrobat will be assuming 
> untagged CMYK means something other than you intended.
> 
> Complicated, isn't it?
> 
> --
> Craig Ringer
> 
> 
> *  You might get away with a good scanner and a quality IT8 reference to 
> calibrate the scanner then build your printer profile from that, but (a) 
> there are issues where the printer & scanner gamuts don't overlap, and 
> (b) it's less accurate.
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