Mitsubishi HC7000 Projector Calibration
We calibrate each home theater that is reviewed. It is a pretty standard calibration, there's always more that can be done by some of the "hi-end" calibrators.
11/19/08 - Art Feierman
Mitsubishi HC7000 Projector - Color Temperature
As mentioned elsewhere, out of the box grayscale balance, is a little warmer than the ideal 6500K. (That means stronger reds.) Here are the measurements:
30 IRE (dark gray): 6017K
50 IRE (medium gray): 6148K
80 IRE (light gray): 6231K
100 IRE(white): 6209K
That's not bad for " out of the box", and it is watchable, but really does need improvement to appreciate the full potential of the Mitsubishi HC7000.
Below we get into the various settings and adjustments, and report on the grayscale balance, post calibration.
In addition to calibrating Red Green and Blue for a correct grayscale balance (6500K), there are a number of other settings that come into play. Typically Contrast and Brightness (white balance and black balance), need to be done first. Color saturation and gamma also need to be adjusted. With some projectors even Tint comes into play, although with most, the Tint control only works with the lower quality inputs (composite and S-video). It should be noted that the Mitsubishi HC7000's gamma settings impact the color balance, so it's important to do the gamma at the same time, or rather, before the final grayscale adjustments.
Our settings (numbers in parens are the default numbers):
Gamma : User mode: High = -1, Medium = -1, Low = 0 (These numbers are based on starting with the Cinema gamma setting.
Contrast: -1 (0)
Brightness: 3 (0)
Lamp Mode: Standard (unless noted otherwise)
Color Saturation: -6 (0)
Tint: -1 (0)
Zoom at mid-range, All other settings at default
Post Calibration Grayscale
The HC7000 produced truly excellent results, with only a 60 degree temperature shift from white to dark gray:
We created our settings in User 1 in the Color Temp area. We used the Warm color temp as our starting point You can choose Warm, Medium or Cool, you cannot start with High Brightness.
The end result of our calibration was excellent:
White (100 IRE): 6490K
Light gray (80 IRE): 6522K
Medium gray (50 IRE): 6425K
Dark gray (30 IRE): 6514K
The color accuracy really showed, when watching the HC7000!
These are the adjustments we made to Red, Green and Blue for the grayscale balance:
Bingo, those new settings cool off the shift to red, and produce an almost perfect balance of red, green and blue, with all measurements within a 100K temperature range!
Brightest mode: Mike does our calibrations these days, and he is more conservative than I am, in terms of dealing with brightest mode. I'll allow a bit more color shift, and other issues, in exchange for more lumens to cut through ambient light, than he does. Still, I have to go by his measurements. You can squeeze out more lumens than he measures, but probably not much more than an extra 10%. He's been doing all the measurements though, since April of this year (2008).
The High Brightness mode produces an image in the mid-8000K range (8401K). This is rather cool, but watchable. Don't expect to see any really rich, bright reds though. There is a slight shift to yellow green, but well within what I consider watchable, when fighting too much ambient light. You cannot adjust the RGB settings for High Brightness mode.
No doubt you can push the HC7000 over 800 lumens with a little tweaking. You would have to start with a different mode, such as the Medium mode, which is in the mid 7000K range, and push up green a bit, sacrifice black levels and allow a little crushing of near whites - all standard stuff for squeezing out more lumens.
Bottom Line: The HC7000 calibrates a great movie mode, and a very good "brightest mode" it's just that, it doesn't make it easy to squeeze out a lot of lumens, keeping the HC7000 in the less bright than average range, when it brightest mode.
For those of you familar, this is the post calibration CIE chart:
Here is a bit of an explanation of the CIE chart, and what it shows, provided by Mike:
The color charts used in our reviews is the CIE 1931 color chart from the Commission Internationale de l’Eclairage (International Commission on Illumination), issued in 1931. As you can see, it displays the full spectrum of light with the primary colors of red, green and blue, as well as combinations of those colors to form secondary colors of cyan, yellow and magenta. The combination of all the colors results in the white point in the center. The chart is depicting a two-dimensional slice of what is actually a three-dimensional color space. The x and y coordinates are the chromaticity (defined by Wikipedia as an “objective specification of the quality of a color . . . that is, as determined by its colorfulness” - ie: saturation and hue) values of the colors. Luminance, which is the darker or lighter shades of these colors, accounts for the third dimension of the CIE color space. Obviously, this cannot be shown on a two-dimensional chart.
Typical CIE Chart
HDTV programming has a specified color space which is depicted by the solid white triangle on this chart. The primary colors of red, green and blue form the three corners of the triangle, with the secondary colors of cyan, yellow and magenta appearing at points along each leg of the triangle. Measured values of the primary and secondary colors appear as a dashed triangle on the chart.
If a projector is perfectly displaying the HDTV color space, its measured values of the primary and secondary colors will directly overlay the triangle. As you can see from the chart above, while the blue corner is close to being correct, the red and green points are clearly outside the defined color space. While this is typical of most digital displays these days (many people like a more “colorful” picture, even if it isn’t accurate), it can result in unnatural colors with some sources. This manifests itself as “sunburned” faces and grass that looks abnormally green. Similarly, if the projector’s measured color points resulted in a triangle that was “inside” the solid triangle, this could result in colors that appear “washed out”. One other problem occurs if the color points lie closer than they should to an adjacent color. This can result in a color like yellow looking to green or too red.
Some projectors have color management systems that can help adjust the saturation and hue of primary and secondary colors to their correct points on the charts. While a proper color management system should also include luminance adjustments, even the two dimensional adjustments can make a big difference in providing natural colors.
So, when looking through the reviews, take note of the projector’s color space and, if it’s not correct, whether the projector offers some type of color management or optional color space settings.