When you export a file to PDF for prepress the CYMK values do not stay correct. Try a spot color and check values in Corel, export to PDF prepress. Open in Photoshop or Paint and check values. They are no longer correct!! This works fine in X4 and makes X5 pretty useless for commercial printing.
I was having major color issues in X5 myself but seem to have solved them so I thought I would share:
I downloaded and installed the free Adobe Color Engine for Windows. (recommended by another user on this forum)
The rendering intents in CorelDraw don't seem to be working the way I thought they should work. I almost always used Absolute since it gave the most accrate color for commercial printing, but when I use it in X5, my whites don't stay white and go to gray or yellow depending on my color profiles selected.
Image of my X5 color settings that seem to be working like a charm:
The one function that is still MISSING is being able to export 8-bit Paletted JPEGs. This option has disappeared in X5s new .jpg Export Dialog.
Hi,
Using Adobe CMM over Microsoft ICM is pretty much a must at the moment on XP systems. ICM 2.0 on XP does not support v4 ICC color profiles which causes a lot of problems, inaccurate colors are the least of them. Using Adobe CMM on Vista or Windows 7 is less straightforward. The color conversion results performed by ICM/WCS vs Adobe CMM ( BPC off ) are almost identical in absolute majority of cases. Adobe CMM has its own very peculiar bugs - e.g. incorrect grayscale processing which forces us to use rathre slow workarounds internally, unstable color conversions to LAB. Still, using Adobe CMM is the ONLY way to bring Black Point Compensation functionality into X5 for those who needs it.X5 renders Absolute Colorimetric intent correctly. Anybody using Adobe apps has to be aware of one interesting twist in their UI - no matter what is selected in "Rendering Intent" control there the Absolute Colorimetric intent is used for real ONLY when "Show Paper White" or "Simulate Paper Color" boxes are checked, and they are unchecked by default. Effectively Adobe apps by default use Relative Colorimetric even though UI might say "Absolute". User-friendly UI at work.Technically Absolute Colorimetric Intent is indeed the most accurate. The fact that it takes into account white paper color makes it useless though for pretty much everything except color proofing. It might be important to see how your content will look like on the real paper, it is rare you want this "paper white" to be used for all white colors in your content..
As for the Perceptual vs Relative Colorimetric intents advice. While David has valid point about the effect Relative Colorimetric conversions might have on content with fine tonal variations another point is missed completely. Choice of rendering intent is not only gamut-specific, it is also content specific. Using Relative Colorimetric intent on fine art raster images might be as disastrous as using Perceptual intent on the vector-based document containing branding colors - Perceptual modifies everything, you can not really "pin" colors you need without resorting to spot inks. This is the main reason Relative Colorimetric intent is de facto industry standard and is used by default in all color managed applicaitons I am aware off, not only ones from Adobe. If you need to change it - fine, but you need to REALLY understand what you are doing, giving blanket advice is unlikely to do any good.
Funny thing you have mentioned 8-bit paletted JPEGs missing in X5... There is no such beast as 8-bit paletted JPEG, it was an UI bogus in X4 which has been finally cleaned in X5. Using 8-bit paletted JPEG option in X4 would first run image through palette dithering algorithm and then output image as regular 24-bit non-paletted RGB JPEG. Net result - much worse quality because of dithering and much bigger file size as dithering kills JPEG compression efficiency.
Gennady
Gennady Petrov said:The color conversion results performed by ICM/WCS vs Adobe CMM ( BPC off ) are almost identical in absolute majority of cases.
Conversions with (assumimg same profilea and test images) CorelDRAW using perceptual rendering and Adobe with the default relative colorimetric with Black Point Compensation are extremly close which is why I have CorelDRAW users choose that. They can always use a different rendering for proofing and print.
Hi David,
David Milisock said:Conversions with (assumimg same profilea and test images) CorelDRAW using perceptual rendering and Adobe with the default relative colorimetric with Black Point Compensation are extremly close which is why I have CorelDRAW users choose that.
Gennady Petrov said:Relative Colorimetric with Black Point Compensation is not equivalent to Perceptual Rendering intent, however they are very close in shadow areas.
Ok when I get to my office I will post some captures and try and explain the difference between the theory and the practicle use of BPC. First off Relative Colorimetric with BPC on does alter colors from the source space that are in gamut for the destination space.
Next the compression of a large gamut space into a small gamut really requires that colors from the source space that are in gamut fo rthe destination space be altered to maintain the overall perception of transition from DMAX to LMAX.
The problem I have is that BPC is not ICC compliant and therefore SHOULD NOT BE USED.
At one point I was thinking pretty much the same way as you do now, and this was one of the reasons BPC is not ( yet) an option in X5. After looking into problem more deeply I have simply realized I was wrong. Do not be surprised if you come up to the same conclusion eventually... But first we have to separate "BPC vs Perceptual intent" arguments from "Relative Colorimetric vs Perceptual Rendering intent" ones, you keep using them together while they are not the same at all.
David Milisock said:First off Relative Colorimetric with BPC on does alter colors from the source space that are in gamut for the destination space.
David Milisock said:Next the compression of a large gamut space into a small gamut really requires that colors from the source space that are in gamut fo rthe destination space be altered to maintain the overall perception of transition from DMAX to LMAX.
David Milisock said:The problem I have is that BPC is not ICC compliant and therefore SHOULD NOT BE USED.
good stuff happening here!.. i will offer a question though - Gennedy, you're arguing the case for BPC very clearly, yet BPC is not an option in CorelDRAW. are we to assume BPC will be added next time or even in an update?
the issue at hand is that Relative Colorimetric rendering of bitmaps does not produce very good results at all for shadows or darks. it will create flat black fields of color where there should be, for example, dark hair with highlights and noticeable texture. in the meantime Perceptual is the only CorelDRAW alternative.
Hi Ghiangelo,
I hope we will be able to add BPC in Draw, however first we have to make sure that whatever we come up with works well. Definitely maybe.
At the moment there are only 2 ways to bring BPC into X5, and the second one is purely hypothetical: 1) download and install Adobe CMM 1.1, select it as active color engine in Default Color Management settings dialog in X5. You can turn BPC on/off in Adobe CMM via their XML configuration file, details are in AdobeCMM Read Me.pdf file installed at C:\Program Files (x86)\Adobe\Adobe Utilities\Adobe CMM
2) Microsoft WCS has black point preservation mechanism built-in, however apparently it will work only in pure WCS color conversion ( both source and target color profiles should be WCS XML-based ones ). Which are non existent at the moment, which makes this path unrealistic.
First let me say that this s a great discussion and thatmy only complaint is that BPC breaks with the ICC rules. Now with that said I wil point this out and then will place some image up in future posts.
A large gamut like Prophoto is at least 70% bigger than any CMYK considering a fixed pixel, so when using BPC 70% of the pixels color is significantly changed while 30% is left unchanged. This IMO causes in some cases issues, it's like a 500LB person lsing 300 LBS in a year. Sure they're thinner but their skin is still too big so they look odd. An od way to explain it but there is no one way nor one correct to compress a large gamut to a small gamut.
Ok I have put about 30megs up on my FTP site, these are files handled as perceptual rendering and WCS and also as relative colorimetric with BPC onand the Adobe CMM.
If you're serious about this conversation e-mal me at davidmilisock@graphictechnology.com I'll send instructions.
OK, lets do it. I will contact you via email to get these test images and see what you are talking about.