Recently I attended the IDEAlliance Proofing Summit held in conjunction with the Publishing Business Conference and Expo at the Marriott Marquis in New York City. During the one day summit I managed to take three pages of notes focused on the meeting’s key topic of Virtual Proofing to the Numbers.
During the initial industry panel a question was raised about how to deal with virtual proofing systems from multiple vendors. Large publishers obviously deal with many printing companies and those companies make use of many of the different virtual proofing systems now available on the market. While it did not seem appropriate to make a comment during the meeting, I will remind my readers that ProofPass.com allows verification of ANY virtual proofing system with centralization of the results on a ProofPass.com internet server.
Bill Pope (of FTA) then spoke about the 2008 Virtual Proofing Systems Certification Program. Bill made a great point that sound color management is the key to successful virtual proofing. While ISO specs inks that most printers are now using, good color management is required to simulate those colorants on a monitor. Bill also made a great point about dealing with proofing disappointment up front. While I loved the comment, I think we all know that customers want what they expect x not necessarily what they see….
A fairly technical overview of the certification program was then provided. I found two items of particular interest during this portion; 1. A shift is being made to utilization of Delta E2000 for virtual proofing verification (already supported in ProofPass.com); 2. One of Bill’s key steps to verify that nothing has been “fudged” by the vendor is almost identical to the ProofPass.com verification procedure.
Some other comments I picked up throughout the day:
- Pressroom monitors will need to be replaced approximately every 18 months.
- Office/prepress monitors should last about three years
- About 90% of the Pantone spot colors can be achieved with a high degree of accuracy on monitors costing about $5,000.
- Grey balance uniformity corner to corner on a monitor is key
- Color clipping on monitors might be overstated – it is localized to fully saturated colors and just results in a slightly duller rendition of the color.
All in all, it was a day well spent with the publishing and agency side of our business.
The most visited post on JimRaffel.com in 2007 is #16 written October 2005 and addressing metamerism. Because of the popularity of this post I have decided to revisit the topic. I will start with some basic terminology and definitions. Then, I am going to present a real world example we are dealing with right now at ColorMetrix.
Definitions: First, metamerism requires a pair of objects. The two objects are often referred to as a metameric pair. In order to be considered metameric the pair must; match under at least one combination of illuminant and observer; not match under at least one combination of illuminant and observer; and have different spectral response curves.
Metramerism Tests: Post #16 shows an example of the GATF REHM indicator used for visual assessment of light sources. This is also an excellent of example of a visual test for metamerism. The two samples may also be measured by a spectrophotometer, and then an instrument test for metamerism can be performed. If the two samples exhibit a small Delta E under one illuminant observer combination, but have different spectral curves that cross at least three (3) times they are metameric.
Our ProofPass.com system was recently used to measure two samples. Below I have provided the L*C*h* values of a ‘Red’ swatch measured on a hard copy proof and then reproduced and measured on an LCD monitor.
| |
Hard copy |
Monitor |
| L* |
40.56 |
43.02 |
| C* |
60.85 |
61.31 |
| h* |
28.44 |
27.9 |
The CMC(2:1) Delta E of the above two samples is 1.34 in a D50/2 degree environment.
Now, take a look at the spectral reflectance and emission curves of the two swatches. (Library Reading = Hard copy and Sample Reading = Monitor)
Again the instrument test for metamerism states that if the spectral curves differ, and cross each other at least three times, then the objects are metameric. The curves look different and I count at least 10 crosses.
As long as the physical sample is viewed in a proper viewing booth, and the monitor continues to be calibrated and also viewed in proper conditions, the metamerism effects of hard copy vs. monitor proofing above should not be a problem. My concerns about this type of metamerism extend to placing a package on a retail shelf which is seldom a D50/2 degree environment.
In #53 I listed a bunch of color resources I had found on the web. I was looking because we are putting the finishing touches on the first beta release of our ProofPass.com soft proofing verification module. For me this project has turned out to be about the journey not the destination. Of course the destination which is a viable commercial release of the aforementioned product that we hope to make lots of money on is not a bad place to end up.
The Journey, however, has been like going back to school for a guy so grounded in the color science of the physical ink on paper side of our industry. I have come to the conclusion that a monitor is just another “black box†that creates color from my perspective. Just like a hard copy proofing system, a conventional printing press, or even a digital printing press is. So, that means if it can be measured it can be controlled.
The key to successful soft proofing appears to lie in the color management behind the system(s). I recently had the opportunity to view and measure eight displays powered by the soft proofing technology of three vendors all in one place. All were powered by Macs, but the displays came from two manufacturers. In our quick and dirty technology demo three of these systems (all under the control of one organization) came in with a very tight peak Delta E of only about 3 between the systems.
Monitors using the other vendors soft proofing technologies fell further out (as the software was pre-beta at that time I am going to omit any further numbers). The verification module did, however, catch that one of the monitors had been profiled to the wrong white point (let’s just say I was pretty pleased with the new toy we built!).
Surround lighting and viewing conditions will make any quality soft proofing system work or not work. I have read papers on subject, I have tested it myself, and I have spoken to people who have done extensive testing of the systems. The less surround lighting (other than your 5000K light booth) the better. The surround and viewing conditions should be identical to the ultimate conditions when you make your monitor profile. One of the biggest factors I have seen to making a good or bad monitor profile is surround lighting.
It is clear to me that monitor proofing is here to stay in our industry, and is also highly viable when properly utilized. While I do not see monitor proofing replacing hard copy proofing altogether, I do see it replacing hard copy proofing in some applications very quickly. In other areas I see monitor proofing replacing many of the internal proofing iterations prior to the hard copy “contract proof†used press side. Much of this is going to depend upon how tight the deadlines are for being able to change copy, and the perceived quality level of the work being produced.
Since #45 in December we have been discussing resolutions to improve the quality of your proofs. In order to gain the full benefit of this installment one should have read and implemented the suggestions in #46 & #47.
Proceeding forward it does not matter if you are utilizing a methodology like GRACoL G7, or a more traditional color management approach. In either case you will include a target on each print job with the same color bar swatches that you output on the proof (#46). This will allow you to measure the press ok sheets and compare them to the proofs, thus building even a larger statistical database to call upon.
When utilizing software like our ColorMetrix and ProofPass.com products for process control and print certification purposes it does not matter if you are using a methodology like G7 or traditional color management. While there are some new formulas out there to run the collected data through the tried and true colorimetric data (L*a*b* and derivatives along with some version of Delta E), do a great job comparing two similar or dissimilar imaging systems.
Unlike density and dot gain values which must be used with pigment sets designed for 4/color process printing, L*a*b* values allow the comparison of an inkjet proof and an offset press sheet. This is possible because we are looking at the actual colors, not values derived from a formula which assumes a certain pigment set.
Not only will you be comparing the measurements of the proof to the press sheet, but you will be building a history of what is a “normal” print condition of each press and paper combination. Some refer to this as finding the “sweet spot” of the printing press.
Overall, as your volume of collected data grows you will be able to refine the system in small steps by reviewing the proofing and press information both independently and together. Using numeric results, charts, and graphs you will be able to see small differences in color that can be adjusted for over time. No system is stable over time, so continuous monitoring is a must in order to maintain stable color.