In the world of colour and colour reproduction the trend is moving towards printing to specifications or standards. This is no surprise to a lot of people but what is less evident is the need to quantify and verify your colour reproduction. As we move towards printing to specific colour specifications it makes the job of verification much easier. Plus, the cost of devices and software required have reduced substantially. I predict in the next three to five years the majority of digital printing devices will have a built-in verification hardware software solution.
But until that happens the majority of printing devices require the user to manually measure and verify. In this article I’m going to give a quick overview of a few of the options available for someone that wants to verify their printing condition. Keep in mind there are a number of different printing conditions and not all are going to target to the same printing specification or standard. It is your job to determine what is the ideal target for your printing process. Once you have identified the best target to aim for, then you need to compare your printing process to the the target. In doing so you will be introduced to a term called Delta E of (also called ΔE*, dE*, dE)
Delta E is not a song from Mississippi
Understanding what this term means is essential for anyone that is making colour measurements and verifications. The simplest explanation for Delta E is a mathematical equation that measures the distance in a three-dimensional colour space between two colours or more simply stated how closely two colours match. A dE from 0-1 is considered a perfect match as our eyes cannot see a difference below a 1. dE of 1-2 is extremely close and the ultimate in colour matching. But a dE this low is not easy to achieve or maintain. It is also important to distinguish the difference between maximum and an average dE. Ideally you want to have an average dE of 1.5 and a maximum Delta E of 5.
I’ve seen manufactures of colour solutions say that they have a Delta E of 3. This number by itself does not tell us enough. We need to know whether the number is an average or a maximum.
Verification in proofing
The first area we’re going to look at is in digital proofing. Here we have two options: built-in or standalone. One can purchase an inkjet with a built-in spectrophotometer. Both Epson and Canon have such printers but the spectrophotometer comes at an additional cost. The built-in device offers substantial advantages as it automates the measurement process. Epson offers the spectroproofer on their 17”, 24” and 44” printers. Canon at this point only offers their device on the 24” printer. I am a big fan of having a device that’s built into your printer. The biggest reason for this is that prepress and print facilities are looking for automation and ways to maximize production. So asking the user to measure proofs takes away a person from his job that can be easily replaced by a built-in device. The reality is with a built-in device it will get done regularly.
If you were to purchase a standalone measurement device the most obvious option is the X-Rite i1 Pro2 Basic. This device is the universal measurement device and costs about $1250 Canadian. The Basic version of this software/hardware combination requires additional software to do the verification. If you have a software RIP driving your device then a verification module is usually available as an add-on module. If not, then ProofPass (www.proofpass.com) is one option as well as SpotOn! Verify (www.spotonpress.com). Both of these third-party solutions offer some insight into how your device is printing as well as a pass/fail function.
Targets and Aim Points
The three main targets, standards or specifications that are in use today are: GRACoL 2013 the de facto standard reference print condition for commercial printing and proofing in North America and other world regions. And SWOP3 & 5 datasets are the de facto standard print condition for publication printing and proofing.
Large Format printing
Verification is not just for proofing it can also be an important aspect of a large format printing facility. Consistency is only possible when you have measurable targets and aim points. If one was to measure directly after the creation of an ICC profile you then would have an aim point for future prints and you could use Delta E to determine if your device has drifted. If the device is still within two Delta E then you know that production can resume. If for some reason your Delta E goes beyond your shop tolerances, you then know that you need to recalibrate your device to bring it back to its baseline.