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!

Or More Appropriately, Process Control SHOULD Never Stop in Color Management

I had an instructor in a class I was taking say, “You can’t have color management without process control.” I thought about that for a bit and decided he was right.

One of the biggest constants in color management for printing is maintenance. The physical condition of the printer needs to be maintained. The environmental conditions of the printer need to be monitored. And the profile of the printer needs constant process control to achieve consistent and predictable color.

Color Management Strategy And Software Is Key

To create a profile and maintain a profile, you need two things: a measuring instrument and verification software to validate the profile. This is a huge part of process control.

SpotOn Verify is a flexible powerful tool that helps you clearly define performance and control your print process. The Visual Match Scorecard shows you how visually consistent devices are. The software provides tracking and trending data to help you print consistently over time.

So, Wait. What’s A Profile?

To have a good color management strategy, you need to understand what you’re trying to maintain.

A profile is a characterization of how a printing device prints at that moment in time. It takes into account all the variables that could affect printing such as environment, media, ink, substrate, print speed and resolution.

Changing one of these variables can negatively affect the quality of printing. Therefore, the profile has to be maintained so that it can accurately do its job.

Process Control Through Verification

After creating a profile for a printer, it can provide great quality print jobs. A couple of months later, the quality shifts in the wrong direction. Many variables such as replacing ink or print heads or using different substrates could cause this shift.

Before deciding to re-profile the machine, print out a control strip, measure it against a specified target and use a verification software system to view the results. Many applications record the status of a printer over time.

Measure charts and keep a trend report to assess printer performance. The shift may not be significant enough to warrant re-profiling the printer or you may find that it’s time to re-calibrate the machine.

If you do regular checkups on the profile of your printer and its performance through verification, you are using process control to maintain the condition of that printer.

The next post will talk about how to use those trending reports in verification software to control printing devices.

For a demonstration of SpotOn Verify, please contact us to schedule a time.

Recently, we have been trying to highlight various features within the SpotOn Analyze and Verify software that both users and non-users may not know exist.

One of those features was Visual Match Scorecard. Another is SCCA or Substrate-Corrected Colorimetric Aims and that’s what we would like to discuss today.

What Is SCCA?

Substrate-corrected colorimetric aims refers to a mathematical formula that approximates the L*a*b* values on a different substrate.

According to the Idealliance site when describing SCCA:

“The value of SCCA in the G7 Master process is that it allows a print or proof made on a non-standard substrate to be judged for its “relative accuracy,” i.e. how it would appear to an observer in the absence of a comparison proof.”

That is why SCCA is referred to as substrate relative.

The SCCA Calculator

A while ago, we helped develop an SCCA calculator for Idealliance. It’s free and anyone can access it. You can view the calculator here.

If you take a look at the image below, you can see that in this example of the calculator we are referencing GRACoL 2013 (CRPC 6). The L*a*b* values of the substrate (first column and row under the Analysis chart) are 95, 1, -4.

On the left, we can choose a test chart, like the TC1617, and measurement condition, like M1. In the fourth option down on that left-hand column, we can alter L*a*b* values for our desired substrate. In this example, we changed the b* value to -6 instead of -4.

Back under the Analysis chart in the second column, you can see how the SCCA calculator adjusted the values for CMYK, RGB, and neutral colors based on the desired substrate’s b* value change.

In the third column labeled “Deltas,” you can see the effect of the substrate change on the CMYK, RGB, and neutral patches.

SCCA in SpotOn

From the SpotOn startup splash screen, you can choose Settings (the wrench and gear icon in the image below).

Choose to change the settings of Analyze/Verify in the top menu and choose Tolerance Sets (highlighted in blue below). The ability to turn on substrate relative or SCCA is one of the options in a tolerance set. We suggest picking an italicized tolerance set (system default tolerance sets) that doesn’t have SCCA turned on (G7 Targeted has it turned on) in the list at left and making a copy of it (duplicate). Then you can turn on the SCCA option by checking the Substrate Relative checkbox and Saving that tolerance set with a new name. I usually add SCCA to the end of the tolerance set name so I know that SCCA is turned on for that tolerance set vs. the original where it is off.

When Should You Turn On SCCA?

When you verify your print and your problem areas are in the whites or lighter colors, it’s often due to the difference between the substrate being printed on and the reference set substrate. Try using the new tolerance set you just made that has the SCCA or substrate relative option turned on.

It’s important to note that substrate correction isn’t always the answer, but it can be a powerful tool in SpotOn Color just like the SCCA Calculator.