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Equipment Used: Orb Optronics SP-100 spectroradiometer Minolta LS-100 luminance meter Klein K-10 colorimeter |
Klein K-10 Colorimeter w/extension tube and rubber boot installed
Professional Grade Calibrations
There is, I suppose, a kind of holy grail when it comes to color analyzers used for measuring the performance of video and film sources. The perfect device would offer reference grade color accuracy, good low-light sensitivity, speed, ease-of-use, and manage of of this while keeping the device relatively affordable. No one device does it all. Spectroradiometers from a variety of manufacturers offer reference grade color accuracy, but they can also be very slow with poor low-light sensitivity, and often cost as much as a new car. Filter-based colorimeters are generally more affordable. They also offer good speed and low-light sensitivity. However, their color accuracy really cannot compete with a 5nm spectro. No device is perfect. However, in my judgment the Klein K-10 colorimeter comes about as close to the ideal that we have been seeking as any instrument that I am aware of. It offers near reference grade colorimetry along with lightning fast speed, world-class low-light sensitivity, and exceptional usability. The MSRP is $7,000. Granted, this is not a budget device, and probably only pros will be willing to spend this much for a color analyzer. However, it is important to keep this in perspective. Even at full MSRP, this is less than half the cost of a 5nm PR-655, and only slightly more than half the cost of a Minolta CS-200 colorimeter.
General Description
The K-10 is the top of the line in Klein's catalog of colorimeters. It is light weight and approximately 10-inches in length and 2 1/4 inches in diameter. It connects to a PC via a serial cable, which ships with an attached USB adaptor. The instrument draws its power from the USB connection so no external power source is needed. It also ships with a diffuser for illuminance readings, a rubber read head boot that will fit snugly against a display for direct contact readings, and a black metal extension tube. The read head boot ensures optimal distance from the display source and offers the added benefit of shutting out external light sources. This offers calibrators the flexibility of taking accurate readings in environments that do not have good light control. This is not a trivial matter. I tested a 75% color patch on a plasma in a dark room and in a fully lit room. In the fully lit room, the color patch was measurably desaturated. However, with the read head boot flush against the screen, the readings were identical to those obtained in a fully dark room. Furthermore, the boot is not adhesive, nor does it place a significant amount of pressure on the screen, so there is no danger of damaging delicate LCD screens. All of this is packaged in a very nice brushed aluminum case. The fit and finish of the colorimeter and the accessories scream quality and are rugged enough for regular field use.
The K-10 will generally be mounted on a tripod. A small metal tripod—apparently designed for use in a laboratory environment—ships with the product. The software that comes with the unit is quite basic, but displays xyY data and plots readings on a CIE chromaticity chart. Despite the physical USB connection, it is a serial device so users must select a serial port prior to use.
The unit also includes 8 LEDs that serve to define the reading area, but these devices have very low light output and are of marginal value. They will not, for example, paint a circle on a display from a distance, which calibrators could use as an effective aiming device.
The Klein in Action
Using the K-10 is simple. I had the software installed and ready to use within five minutes. All the user has to do is select the correct port on the PC, load the desired calibration files (the Klein ships with files for LCD, CRT, and DLP in illuminance mode), and then simply click the Measure Color button. The K-10 automatically enters continuous mode while reporting a string of results until the user clicks Hold. Oddly, the only readings the Klein software takes are continuous. It is not currently designed to take single readings at all. The reported results are returned instantaneously and are extremely consistent. For those accustomed to seeing readings bounce around, this is a welcome experience.
Most users interested in video calibration will probably want to use the Klein with software optimized for that purpose. Currently, Calman supports the Klein and ChromaPure will offer support in its next major release.
The K-10 appears to be designed for use primarily as a contact device. However, I also used it to take readings directly from a front projector's screen with good results. This is one application where the lack of a true aiming device was missed. In practice you can place the K-10 close enough to the screen that aiming is not an issue, but I would not attempt to use it to take readings from near the seating position as I am accustomed to doing with other non-contact devices. I did not test it with the diffuser in its illuminance mode. SMPTE guidelines specify that readings should be taken directly from the screen, and direct lens readings would have to be corrected with an offset in any case. In any event, the K-10's phenomenal low-light sensitivity makes a direct lens reading is unnecessary in the vast majority of cases.
Performance
I have already commented on the K-10's speed. It low-light sensitivity seemed equal to, or actually exceeding, my reference Minolta LS-100. I was able to get consistent black level readings from a Pioneer Kuro plasma that agreed with the Minolta to within 0.001 cd/m2. I didn't have any other display with a lower black level to test it on, so the full extent of its ability to measure low light sources remains unexplored.
For most calibrators, though, color accuracy is the decisive factor for any meter. It does not matter how fast or how low a device reads if the color accuracy or repeatability exceeded acceptable tolerances. I tested the K-10 on a Sony CRT, a Sharp DLP front projector, a ViewSonic LCD, and a Pioneer plasma. After each run I immediately took measurements from the Orb spectroradiometer and then compared the results. I was satisfied that the Klein's luminance readings were reference grade, so I compared the chromaticity values only. See the table below for details.
Color Differences
Comparisons and Conclusion
For a filter-based device, this is exemplary performance. There were occasional bumps in accuracy, but the average error with four different displays never exceeded xy0.006 or CIE94 1.2 for color or xy0.006 CIE94 2.9 for white. These results are somewhat better than what I see with the i1Pro spectrophotometer and the Chroma 5 colorimeter, the only two sub-$1000 color analyzers I would consider even minimally acceptable for professional work. Of course, the Klein costs many times what these devices cost, so the small increase in colorimetric accuracy and the rather substantial increase in usability make the K-10 suitable only for those who are willing to pay a lot more for that extra nth-level of accuracy. The only other sub-$10,000 devices that I know of that could improve on the K-10's color performance are the Orb and perhaps the Microspec (both spectroradiometers), and neither of these devices can come anywhere near the K-10's speed or low-light sensitivity.
Perhaps a better comparison would be the X-Rite Hubble, which offers a similar design to the K-10 at a somewhat lower price. The Hubble is also very fast and consistent and it provides excellent low-light performance as well. One other appealing aspect of the Hubble is that—unlike the K-10—it provides an effective aiming system for distance measurements. However, the Hubble's color accuracy falls short of the K-10 and the Hubble requires both an external power source and regular dark level readings to maintain its accuracy. The K-10, like the Chroma 5, requires no dark reading at all. For myself, requiring the user to perform periodic dark readings is close to a deal-breaker. The amount of extra effort this adds to a long calibration is not trivial, and perhaps explains why I never really warmed up to the i1Pro, despite its many obvious virtues.
As you can probably tell I am a big fan of the Klein K-10. It is not perfect. It cannot, by design, offer true reference level color accuracy, though it comes tantalizingly close. It also needs an effective aiming system before it will seem entirely at home in the home theater calibration market. I could pick some nits as well. I would prefer a longer cable for placement flexibility (the Hubble's cable is much longer) and/or a cable that detaches at the meter end, rather than being hard-wired onto the device. Try screwing an instrument with a cable attached onto a tripod without getting tangled up and frustrated and you'll know what I mean.
No other sub-$10,000 instrument I have tested offers the mix of accuracy, speed, low-light sensitivity, ease-of-use, and high build quality of the Klein K-10. I have added the K-10 to my inventory of essential calibration tools for regular use in the field. Version 2 of ChromaPure, scheduled for release in the first quarter of 2010, will provide support for the Klein K-10.