# Why the C6 from SpectraCal



## mechman (Feb 8, 2007)

From SpectraCal:

We started working with X-Rite just about two years ago on what is now the D3 family. We flew to the X-Rite facility in Ames Pond and had meetings with their color scientist team including some of the guys from the original Sequel Imaging group. With us we brought a long laundry list of requests we felt the industry was going to need in the near future as display technologies were rapidly changing. Some of those requests were: 

•Low light support;
•Repeatable results;
•Integrated tripod mounting thread;
•Built-in diffuser with enabled detector for diffuser placement;
•Design built for highly polarized angular light;
•Sealed optics and sensors;
•Field upgradeability;
•And narrow field of view.​
We requested the ability to read at low light and repeatable results because displays and projectors were producing blacker blacks than past technology could achieve. The integrated tripod mount was needed because the displays were getting bigger and hanging the meter cord over the top of the display was not a good option anymore, and because front projectors were becoming more popular. Accessories or components could get lost or misplaced, so an attached diffuser with detector to tell us if it was properly in place. A design that dealt with highly polarized and angular light that LCD manufacturers seem to be doing to focus more light into a narrow vertical but wider horizontal viewing area. Sealed optics and sensors to minimize drift over time. The ability to add display characterization to the meter once it was in the field to help ‘future proof’ the meter. A narrow field of view so that it could read from a front projection screen. 
The extraordinary engineering work the X-rite team performed on the D3 family made huge strides in overcoming the two main reasons meters become obsolete: filter and sensor drift, and the increasingly radical changes in the spectral characteristics of new displays. Both of these problems are interrelated. 
You need a very stable and accurate filter sensor array to solve the drift over time issue and once that was solved you can take advantage of it. With a stable and accurate filter sensor array you can characterize each meter at the factory with a high degree of accuracy. 
The second thing that can make a meter obsolete is changing display technologies specifically to the spectral response curve. Here is an example of a spectrum sweep with the 1931 2 deg standard observer curve on it from a LCD CCFL.

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A tristimulus meter through its filters and sensors tries to mimic the standard observer curve, in this case the 1931 2 degree Color Matching Function (CMF). If all display spectral response curves matched and the filters in the meter also matched the 1931 2 degree standard observer, we would not need to calibrate or characterize the meter. But in real life the meters’ filters are never perfect and have deviations. Also we have not seen a display that perfectly matches the 1931 2 degree standard observer. So in the past we had to create a calibration table for each major type of spectral response curve to cover our bases. As part of that processes of creating additional tables for each spectral response curve it also took into account the deviation in the meter’s filters. This is how it’s been done for a very long time and is the recommend method by NIST for calibrating a tristimulus device. But now that X-Rite has eliminated the need to deal with the filter sensor deviation, we can solely concentrate on just the display spectral response not matching the standard observer curve. So with a highly stable and factory characterized meter and the ability to add display characterization data outside the factory you have a field upgradable tristimulus meter.

As part of the work with X-Rite we worked out a deal to be able to provide these field upgrades with the SpectraCal C6. Our in house lab that does all of this work is quite extensive starting with our Konica Minolta CS-2000 which is only one of two devices used by X-Rite for this work, the other being a CS-1000. The lab is temperature, light, and humidity controlled. Each display device has gone through a rigorous process of testing before being used in the lab and is calibrated before each meter or research run. The mechanical jigs used to line everything up for calibration or testing is controlling tolerance down to or even some times less than 1mm and less than 1 degree of angle.
The SpectraCal C6 is truly a state of the art tristimulus meter that has been in development for over two years. It comes with a NIST certificate of performance. It can be field upgraded for newer display technologies. It has a built in tripod mount and ambient diffuser, large optics, filters and sensors that deal with off angle light, a narrow field of view and improved low light capability


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