In our last post, we discussed how you can use our SpotOn Verify software to compare a measurement of a printing device to a reference such as GRACoL 2013. While there is nothing necessarily wrong with this approach, using a custom reference could be more useful.
The Problem With Using RPCs
Reference print conditions (RPCs) such as GRACoL 2013 can be helpful as an aim or target to achieve because they are based on a composite of different devices. Therefore they are achievable targets. Because of this, they are generally accepted throughout the printing industry.
The problem is that there isn’t a reference print condition for every printing process. Often you are trying to aim your printing devices to a reference that isn’t for your industry. An example would be printing signage on vinyl using GRACoL 2013, which is an offset on coated stock reference and not inkjet on vinyl.
In Tolerance, But Not Consistent Color
Another issue is that being in spec to an industry standard doesn’t mean that your printing device is producing consistent color. At no time can you actually hit the bullseye of the target to which you are aiming. It’s just not possible. The results will always be a bit off.
What happens if you are off to the left one day by an acceptable amount (within tolerance) and the next day you are off to the right by an acceptable amount (again, within tolerance)? Both prints are within tolerance to the target, but they are off to each other by more. This becomes a color shift that you and your customers can see.
Bonnie and Clyde
As an illustration of this, we often refer to our Bonnie and Clyde scenario. In this instance, Bonnie and Clyde were two separate printers of the same model using the same inks and substrates and printing the same jobs.
The client was frustrated because when each machine was measured and compared to GRACoL, they both were within tolerance to GRACoL based on industry standards. However, the two printers were visibly not printing the same. How could two printers that were both within accepted industry tolerance of GRACoL be producing such obvious color differences?
The answer can be determined by these bullseye charts. As you can see, the two printers are both within a reasonable range of the GRACoL standard. But just because they are both within that range of GRACoL doesn’t mean they are in a reasonable range of each other.
Take a look at this second bullseye chart below in which we compare Bonnie and Clyde to each other instead of GRACoL.
In our client’s situation in which they desired their two printing devices to produce consistent color, it would make more sense to measure and compare the two machines to each other than to an industry reference.
Monitoring A Single Printing Device
This same methodology works in a situation where someone wants to monitor a single printing device over time.
Once you have that device where you want it (usually targeting some industry reference like GRACoL), take a measurement and make that your baseline for comparison in SpotOn Verify. Continue taking measurements comparing each measurement to the new baseline you created. The resulting charts SpotOn generates will show you exactly how much your printing device drifts away from that baseline you created.
The next step is to establish tolerances for the amount of drift. When the device drifts outside those tolerances, take corrective action (usually maintenance or recalibration of some sort depending on the device) to get it back in tolerance.
Color Management Is A Process
Managing color is a process that needs to be verified on a regular basis. The goal should be to keep color consistent.
To do this, it is necessary to create a realistic baseline or target. This realistic target should be based on how your device prints on a given substrate in your shop.
Monitoring the device to itself in this fashion will result in graphs in SpotOn that show the variation of this device to itself over time. If you define a reasonably tight tolerance, you can keep your device printing visually consistent over a very long period of time.
Of course, you can make this process more robust by monitoring multiple printing devices to a single reference like the Bonnie and Clyde example. You can also use this method to determine how much of a difference there is when switching to a different substrate. Sometimes you can find that several substrates print similarly, yet others can print very differently.
By making these comparisons using your custom reference, you can determine which substrates will require their own calibration and profile. Plus, you will learn how much substrate contributes to color differences.
Ready For A Demonstration?
If you would like to learn more about how SpotOn Verify can help you produce consistent color with your printing devices, we would be happy to give you a free online demonstration. Contact us to schedule a date and time!