Archives for October 2012

After my recent post about the new ColorBase version, a friend asked the question: “why is it better than factory calibration?” I though this could be interesting to other people, so here’s my (longish) answer.

Some background first. In the grand scheme of things, building a color profile for a device is a two-step process. The first step is calibration, which sets the basic operating parameters of the device to a well known (sometimes standardized) default. In case of monitors, calibration sets the black level, white luminance, color temperature and tone reproduction curve. In case of printers, it sets the relationship between color values and the actual amount of ink laid down to be linear – this is why this step is called linearization. The second step is the actual profiling. Here the software determines the color reproduction characteristics of the device and creates the profile.

On the low end, manufacturers tend to skip the calibration step, doing only the profiling. This is a nasty trick and the reason why I think that cheap colorimeter packages that can’t do the calibration step are downright dangerous and actually worth nothing. On the high end profile making is always preceded by calibration.

Speaking of printers: the lack of calibration (linearization) is less noticeable here, because profiling packages do a linearization step under the hood before starting to build the profile. This is not that accurate as the separate step, however (“true” linearization controls parameters in the rasterization process, whereas “simulated” plays with the color values). So basically it is more or less done for printer profiles.

My favorite example for showing color reproduction differences across devices is the TV department of your favorite electronics store. Almost every single one displays the same content differently. Consumer printers are the same. Take two Epson 2880s, and they will print different colors. In case of professional Epsons, all the devices are “factory calibrated” to be as identical as possible when they leave the factory. But this does not mean that they will not drift over time! And because of this drift (and inherent difference in consumer models) you’ll have to re-create all the profiles from time to time. Which could be a daunting task.

To be able to decide whether your device drifted out of tolerances, high end profiling packages provide a validation tool that measures the color reproduction accuracy of the calibrated/profiled device. This way you can check the status periodically and recalibrate/re-profile as needed – instead of doing this blindly every month or so.

Epson’s ColorBase is a software for both linearizing the printer driver and a validation tool for checking the linearization accuracy. A welcome extra is that it can do this for higher-end consumer printers. So one can utilize ColorBase in two different ways:

• Use it to measure accuracy, and redo the complete linearization/profiling for each of the papers when the accuracy has drifted. This could still be daunting for several papers, but this provides the utmost precision.
• Use it to measure accuracy, but only redo the linearization if the printer became out-of-spec. Because ColorBase returns the printer to the state it had been before creating the profiles, there are pretty good chances that the profiles will remain accurate.

I have been using the second method for five years with great success. And the longest period that the printer was in-spec reached 2 years with my late 4800. This demonstrates that we are talking more about peace of mind and process control here than visible results. This stuff is about to catch when something goes wrong before it ruins several prints.

And what’s the difference between factory calibration and ColorBase? Actually they are two different things. Factory calibration is for making sure that pro printers are identical when they leave the assembly line, whereas ColorBase is a tool for employing process control.

I must mention two glaring omissions in the package, however. Ink limiting and support for third party papers. You can control ink within the printer driver to some extent, but this should be done with the linearization step. Over-inking could be a serious problem using the driver with some papers. Not supporting third party papers could be worked around by linearizing the printer to the Epson paper selected as the media type for the third party paper (for example Velvet Fine Art in case of Hahnemühle Photo Rag). You will not have a linearization for Photo Rag (which would be the desirable), but at least you’ll be able to build its profile on a solid and consistent base.

If you need ink limiting and linearization for custom papers then moving to a RIP is the only solution these days.