Spectro vs. Colorimeter
Spectro vs. Colorimeter
- Subject: Spectro vs. Colorimeter
- From: email@hidden
- Date: Tue, 30 Sep 2008 15:56:26 +0000
Hi to all,
The DreamColor display and other displays that use RGB-LED backlight are particularly challenging to calibrate. The problem arises because the Green LED has a center wavelength in the 520-530 nm range. The leading edge of the emission spectra is very close in shape and location to the leading edge of the Y color matching function. Small differences in wavelength calibration and bandwidth can easily result in some very large differences. A typical difference between a PR650 and Minolta CS1000 can be almost .01 in xy. The CS1000 has half the bandwidth of the PR650. I don't think that I would rely upon an i1 or Munki to have the precision to make this measurement with any certainty, but they would probably measure closer to the PR650 than the CS1000.
One should also note that the same factors that make the measurement difficult, also enhance the probability of observer metamerism. It will be interesting to see if this is a factor in print to screen matching. In this case you could have two observers disagree on the screen image match. We're running some controlled experiments at X-rite and we'll see if detect any issues.
With regard to third party calibration of the DreamColor Display. I can safely say that calibrating this display is no walk in the park. You have to interface to the back light servo to set white point and luminance and while the shaper-matrix lut generation is trivial for your average color scientist, programming that lut into the display requires a great deal of very undocumented DDC interaction. Any third parties would have to have a very strong working relationship with HP. It's a lot of work..... If any of you have requests for features for the DreamColor line, you should contact HP and request them.
Take care,
Tom
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