> 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. > _______________________________________________ > Scribus mailing list > Scribus at nashi.altmuehlnet.de > http://nashi.altmuehlnet.de/mailman/listinfo/scribus
