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  • Relative vs Absolute

    Hello!

    We just got a new Epson 4800 along with the EFI ColorProof software. Our printers are giving us their icc profiles and we are trying to create a workflow for each. When I run the proofing chart (with all of the squares), I noticed that the printer has added a substrate tint (in one case a tint of yellow). I optimize and measure the proofing chart and add this to my workflow. When I go to actually print something using this profile I have a choice of rendering intents; Relative or Absolute. I prefer the looks of the Relative intent, but it seems like I should be using the Absolute intent. The Absolute intent always looks so flat and the highlights have weird cast to them. Any advise on this?


    Thanks in advance!
    Kirsten :-)

  • #2
    Re: Relative vs Absolute

    For production files (files going to prepress or printer), always keep as RGB and embed the ICC profile and let the printer do the conversion, or convert/build in press ICC profile. These conversions use Relative Colorimetric Intent.

    Absolute Colorimetric Intent is used only in proofing, and not at all times. For instance, if you have a printer capable of really small dots (where you can't see the dots on the proof), then you may want to use Absolute Colorimetric Intent. However, if the printer doesn't have enough nozzles and you see the paper simulation of the press paper as dots on the proofer paper, then you would want to use Relative Colorimetric Intent. If your proofer paper is about the same color as your press paper, then you'll want to use Relative Colorimetric Intent.

    I have tested my proofers, and when I use the official GRACoL2006_Coated1v2 (which my press is set up to match) as source, and have my custom proofer profile set as destination, with one proofer using Relative Colorimetric Intent for the conversion from press to proofer profile, and one using Absolute Colorimetric Intent for the conversion from press to proofer profile, I have not seen much of a difference at all. In fact, you'd really have to have a critical eye to be able to tell a difference.

    Don

    Comment


    • #3
      Re: Relative vs Absolute

      Hi All,

      Oh the joys of Absolute vs Relative Colorimetric settings for proofers. To my mind, both have limitations for hard copy proofing. Not only do you get the afore-mentioned problem of small dots for Absolute Colorimetric, but for Absolute Colorimetric you also you have no way of knowing if the colors you are seeing on print are in gamut and so accurate. If you switch to using Relative Colorimetric, sure you know that the colors you are seeing are not accurate (by definition, since the gamut has been re-mapped to match white points), but then you just know that they are not, or are close, as the case may be if you're lucky.

      To me that's a clear benefit of color accurate virtual proofing. In our recently released FirstPROOF v5, with our new innovative method of doing Color Management (that is fast, simple and easy), we always use Absolute Colorimetric Intent. So what you see on screen is color accurate, with no issues regarding small dots. That is, it's as accurate as your monitor allows. And if you want to know which colors you are seeing are in gamut (for your monitor) and accurate, you simply click on the Gamut Check Tool and hey presto, all the colors that are out of gamut (on your monitor) go red. If that's not good enough, then you can simply replace your monitor with one with a wider gamut, such as the Eizo CG241W/CG221 or Samsung XL24 and now many more of your colors (if not all) are in gamut. But the main thing here is that you know this.

      Personally, I think the 80s to 90s were all about Chromalin proofs, the 90s to 2000s were all about inkjet proofs, but the next 10+ years will be all about virtual proofing. There's so much more you can do with virtual proofing than you can with inkjet proofs, with none of the hassle of broken inkjets, jammed paper, 3-5 minute print times, cost of inks, cost of paper, space requirements,...

      And forget about spending hours profiling printers by printing large charts with 1000s of patches and reading them with expensive automated spectrophotometer. That's history - or will be for users of FirstPROOF Pro v5 with our breakthrough CM solution, which we're applying for a patent on.

      PS If you've not heard about the breakthrough we've recently made in virtual proofing and color management, it's well worth a read as it will fundamentally change how proofing is done. Or that's what we believe. Take a look at http://www.hamillroad.com/main/produ...proofcolor.htm and the 'guide' that you'll find there.

      Regards,

      Andy.

      Andy Cave,
      Chief Executive Officer,
      Hamillroad Software Limited.
      www.firstproof.com
      www.hamillroad.com

      Comment


      • #4
        Re: Relative vs Absolute

        The responses to your questions have all been good. Relative colorimetric is used more frequently since it maintains a closer relationship between the in-gamut colors. even if it produces out of gamut colors. The white point of one color aligns with the white point of another in this rendering intent. The white point shifts because it needs to align with that of the light source or paper tint used. Use relative colorimetric if the destination gamut is narrower than the source gamut.

        In absolute colorimetric, the colors are preserved, without the white point changing. Unfortunately, this also produces colors that appear flat as the white point of the monitor will not adjust to differences in the white point of the paper. Absolute colorimetric is useful for instances where the destination gamut is wider than the source gamut.

        Check out these resources for more info:

        http://www.amazon.com/Understanding-...507288&sr=1-10

        http://www.amazon.com/Exploring-Digi...4144963&sr=8-1

        Comment


        • #5
          Re: Relative vs Absolute

          Andy,

          When reading the webpage that you gave a link to, I see that you:
          1. Calibrate and profile monitor.
          2. Don't have to spectrally profile the press to get the press/paper/ink characteristics, but just take a few or several readings to get the important data. This is done instead of doing a press run to get data to build an ICC profile.

          I can see that it would save time for someone who didn't have an ICC profile already, or are not using a standard profile. For me, I would calibrate my monitor, set up the press via G7 method (using IDEAlink Curve software), and use the official ICC profile to view my stuff in Adobe programs (or Quark for that matter) to know what I'm getting. I have DotSpy to look at screened plate files, but I rarely use it (because I rarely have a need to).

          I guess what I'm saying is that I already have the functionality that this new stuff in FirstProof gives. Maybe not the exact same way, but I get an accurate soft-proof using ICC profiles. Freely available, official profiles.

          Now, the only way that I could see your product as useful to me perhaps, is if it could take my unscreened files and ICC profile (files printed in the past) and repurpose them via altered TVI curves to look the same on GRACoL2006_Coated1v2 or ISOuncoated as they have on my existing printing condition. Overall, I don't see a need to even repurpose this way, but I want to keep an open mind because not all colors are gonna match when not repurposing. For those few colors that I would need new CMYK values for, my present gameplan is to scan with an Eye-One Pro a previously printed piece, and using color management (Relative Colorimetric Intent w/BPC) to get new CMYK values from the given Lab values.

          Also, when I proof the same CMYK values to my Sherpa 2 (Relative Colorimetric Intent) and to my Epson (Absolute Colorimetric Intent), although the gamuts and inks are different, there is so little difference in appearance between the two (because both proofers have been calibrated with a spectro), that one would have to have a VERY color critical eye to see the difference. So here again, I have something that works really well and you can't really see a difference between proofs using the different intents. I say this is because (as my Excel calculator confirmed), that:
          U.S. We Coated (SWOP) v2 (Relative Colorimetric Intent to Lab to get NPDCs of unprinted, because we don't print on SWOP paper although our seps come in SWOP)
          GRACoL2006_Coated1v2 (Absolute Colorimetric Intent, to show printed Lab values to plot NPDCs)
          GRACoL2006_Coated1v2 (Relative Colorimetric Intent - because separations are actually done using this intent and not Absolute Colorimetric - and getting Lab values to plot NPDCs)

          All lined up real close to each other and the NPDC graph's NPDCs. This is why you can't tell a difference hardly at all. The same can not be said for other profiles I tested. Other profiles I tested had different NPDCs when using Relative Colorimetric Intent vs. Absolute Colorimetric Intent. This is one main reason I like the official GRACoL2006_Coated1v2 ICC profile (other than it just makes sense for people to get on the same page so that designers can know what the print will look like no matter where they get their job printed).

          Don

          Comment


          • #6
            Re: Relative vs Absolute

            Hi Don,

            > When reading the webpage that you gave a link to, I see that you:
            > 1. Calibrate and profile monitor.
            > 2. Don't have to spectrally profile the press to get the press/paper/ink characteristics, but just take a few or several readings to get the important data. This is done instead of doing a press run to get data to build an ICC profile.

            Correct, although we use slightly different language.

            When you profile the press you're having to completely profile every single color combination (or a set of colors large enough that the color engine can accurately interpolate between them). Not only do you have to print/measure lots of colors, but the profile that this results in contains either XYZ or Lab data. So it's really a color profile. If you are printing more than 4 inks, such as CMYKOG, then you have to print and measure even more patches - the more inks you use, the worse it gets.

            What we do is read the spectral data of the paper and inks (which result on the press); this involves only 5 readings (for CMYK), plus another 4 if also setting up for Dot Gain (and another 3 if setting up for ink trapping) - all taking less than 60 seconds or thereabouts. We then take this spectral data and combine this with a physical model of printing to 'profile' the press. So the 'profile' that this results in contains true Spectral data. So we call it a spectral profile (as opposed to your [ICC] color profile).

            Doing it this way has the benefit that we don't need to do a press run to get the data to build an ICC profile (we simply read our data from the color bars), and we don't have to read 1000s of patches to create an ICC profile. It's a much faster method that can use inexpensive equipment (such as the Eye-One Pro - no need for the Eye-One IO to automate it).

            > I can see that it would save time for someone who didn't have an ICC profile already, or are not using a standard profile. For me, I would calibrate my monitor, set up the press via G7 method (using IDEAlink Curve software), and use the official ICC profile to view my stuff in Adobe programs (or Quark for that matter) to know what I'm getting.

            Sure - if you have an ICC profile already for your press, then you've already got that. Only a few standard profiles exist and they are also limited - they only cater for a couple of paper types and inks and typically for CMYK only. If you start using spot colors, then you can't really use a standard profile (any overprints of process with spot colors and you've no idea what you're getting with standard ICC profiles). If you start printing on non-standard paper, or card, or plastic, then again you can't use a standard profile - they don't exist.

            Having said that, it's quite possible (in lots of ways) for your PDF proof to not match a plate proof (but that's another long discussion). That's always been the argument for a ROOM based workflow. And with FirstPROOF this is exactly what you are getting - a ROOM based color accurate proof, with in addition powerful tools to check lots of pre-press issues. Any change in screening for example, from AM to FM likely invalidates your ICC profile and means you won't get a match. The beauty of our system is that it works whatever your screening - HPS, Balanced Screening, Stocastic, etc... - with only one set of measurements. You can mix screening in a single job and we'll accurately proof it.

            > I guess what I'm saying is that I already have the functionality that this new stuff in FirstProof gives. Maybe not the exact same way, but I get an accurate soft-proof using ICC profiles. Freely available, official profiles.

            So you have freely available standard profiles for all your paper, card, plastics, inks, etc..? If you only print CMYK on one or two types of paper, then sure you can do this. Otherwise, not.

            In addition, although you see a color accurate soft-proof using ICC profiles, my guess is that you are doing this on the source PDF file. Once you print it, you might get different results. Lots of things can happen, but these depend on what happens once you submit your PDF file for print. As said before, that's another long dicsussion on the issues facing pre-press and press.

            > Also, when I proof the same CMYK values to my Sherpa 2 (Relative Colorimetric Intent) and to my Epson (Absolute Colorimetric Intent), although the gamuts and inks are different, there is so little difference in appearance between the two (because both proofers have been calibrated with a spectro), that one would have to have a VERY color critical eye to see the difference. So here again, I have something that works really well and you can't really see a difference between proofs using the different intents. I say this is because (as my Excel calculator confirmed), that:
            > U.S. We Coated (SWOP) v2 (Relative Colorimetric Intent to Lab to get NPDCs of unprinted, because we don't print on SWOP paper although our seps come in SWOP)
            > GRACoL2006_Coated1v2 (Absolute Colorimetric Intent, to show printed Lab values to plot NPDCs)
            > GRACoL2006_Coated1v2 (Relative Colorimetric Intent - because separations are actually done using this intent and not Absolute Colorimetric - and getting Lab values to plot NPDCs)

            Now here is exactly where you can use FirstPROOF Pro v5 CM to save you time and money. Since you can RIP your job to produce your plate data (TIFF, PGB, LEN or RAS) and then color accurately view that plate data with FirstPROOF, you don't need to do any hard copy proofing; you make the plate data available to the press guys, so that they too use FirstPROOF on a high-end monitor next to the press and this is what they print to.

            It's exactly this that we're getting a lot of interest in. Pre-press use FirstPROOF as they've always done to QA their jobs before printing (checking content, blends, vignettes, screens, moire, inking, traps, seams, bar codes, spot colors, orientation, etc...). This saves them time and money by picking up problems with jobs that they could not catch at the PDF stage. Pre-press also then get to see a color accurate proof using FirstPROOF. When they've finished and release the job, the press guys also use FirstPROOF and get to see exactly the same color accurate proof (that pre-press saw) and this is what they print to. No need whatsoever for a hard copy proof on a slow output device. The more people you have sharing the hard-copy device, the better FirstPROOF gets, as each pre-press person can indepedantly use the power of their own computer to get on with checking and proofing their own jobs.

            Regards,

            Andy.

            Andy Cave,
            Chief Executive Officer,
            Hamillroad Software Limited.
            www.firstproof.com
            www.hamillroad.com

            Edited by: Andy Cave on Dec 14, 2007 8:33 AM

            Comment


            • #7
              Re: Relative vs Absolute

              Andy,

              Thank you for your thorough response. With spot colors, I can see the benefit over what I currently have. Otherwise, I already have a ROOM workflow (although I'm looking at a ripped file, not screened, which is no problem for me because we've had no problems on press with our screening). I understand screening from AM to FM would cause color shifts. Of course the press would have to be set up via G7 again if screening changed. But then I could still use the same official ICC profile (calibration changed to keep ICC profile relevant, just like in other devices in color management workflow). as far as printing on different paper types, they are so close to the coated and uncoated that I can proof for only coated and uncoated. For instance, I make a coated proof for a job that's printing on plastic, and the pressman uses lower Cyan density than normal to match the proof.

              Having said that, I agree that monitor proofing is the future, although at this time I make hard copy proofs for our customers as much as for pressman. Although, it will take someone better than me to sale the boss on monitor proofing. I can't make up my mind on about anything these days, so I stay with what works for me for many years so far.

              Don

              Comment


              • #8
                Re: Relative vs Absolute

                Hi Don,

                There's actually one more benefit of our system that I forgot to mention - re-profiling.

                How often do you re-profile your system? Every day? Every week? Every month?

                With our Spectral Profiling method that uses a small number of readings from the color bars around the outside of the job, you can re-profile every day, in less than 60 seconds. Or whenever you want - you just take the last job you printed, take 5, 9 or 12 quick measurements, and voila you've re-profiled.

                Regards,

                Andy.

                Comment


                • #9
                  Re: Relative vs Absolute

                  Andy,

                  We haven't re-profiled once since we set it up years ago. Press sheets still match the original profiles we made for coated and uncoated.

                  Don

                  Comment


                  • #10
                    Re: Relative vs Absolute

                    > What we do is read the spectral data of the paper and inks (which result on the press); this involves only 5 readings (for CMYK), plus another 4 if also setting up for Dot Gain (and another 3 if setting up for ink trapping) - all taking less than 60 seconds or thereabouts. We then take this spectral data and combine this with a physical model of printing to 'profile' the press. So the 'profile' that this results in contains true Spectral data. So we call it a spectral profile (as opposed to your [ICC|http://printplanet.com/discuss/] color profile).
                    I see here, Andy, that your breakthrough is based on the usage of spectral data. I also read that you are applying for a patent. I'm am sure you realize that you are not the only one measuring spectral data. EskoArtwork Kaleidoscope for example, also left ICC profiles behind. We have the possibility of measuring a profile with 1 measurement for each ink + paper base, just like you do. We offer this for customers who want to spend little time on profiling.

                    By default we aim for better quality. Thus measuring a profile with more patches. Not all possible combinations but well chosen combinations. We do this both for CMYK insets, CMYK+extra inksets or any custom combination of inks you desire. Also these profiles are made storing the Spectral data.



                    For those that aim for best quality, we even go further. As presses tend to have fluctuations over time (first sheet-last sheet) and large offset presses have fluctuations regarding the position on sheet, we offer the ability to merge multiple measurements to 1 average profile. Investing in even more measurements for better color.




                    Another advantage of spectral data: you can select your illuminant in the last step of the process. If you are working in D50, but you are curious how your job looks like in supermarket conditions, you just switch.



                    It is my personal believe that you get much more confidence from your customers when you can actually give them something in their hands. Some samples that they can take along, compare with previous jobs. Due to the emissive nature of a monitor, you will not reach the same look and feel of an actually folded mock-up in your hands. Remote proofing is just the opposite qua investment than soft proofing. Yet I believe it has I brighter future.

                    Comment

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