AVS Special Member
Join Date: May 2008
Location: San Francisco - East Bay area
Mentioned: 1 Post(s)
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Quoted: 18 Post(s)
Whenever you have the ability to calibrate from the screen, you should do it. ALWAYS! No room for discussion. The screen changes the light. If you calibrate directly from the projector, you aren't compensating from any color shift the screen causes, and yes, it can be VERY significant. One popular screen material adds about 600K of blue to everything. If you make the mistake of calibrating the projector (meter aimed at projector) without the screen, the images will always be too blue with that screen material. Some other screen material might lead you to images with some other color bias. And if the meter is not placed on your viewing axis, you may get mislead with inaccurate luminance measurements (most critical for medium-to-high gain screens). If you are trying to get 16 fL but can't, it may only be because the meter is not on the same axis as your eyes (if you have a screen with some gain).
I find the comment that it can be tricky to keep the meter out of the light path may or may not be true depending on the meter. I have zero trouble keeping my large-ish meter out of the light path. In fact, it is no more difficult than keeping my head out of the light path. But my meter has a 1-degree field of view so it can be placed near the main seat. So I set it up at the same height as my eyes and at a distance I view the screen from (or even farther) and make sure the axis of the meter matches the viewing axis.. If your meter has a wide field of view that requires placement close to the screen... well, that's just not the best sort of meter to use for projector calibration. Though you should STILL be able to do it OK, but it may take some time to find the right setup. Once you find the right height and angle for the tripod, it would be useful to mark the tripod so you can replicate everything next time you setup without all the trial and error.
Frankly, the light coming from the projector is a non-issue. What is important is the light you see from the screen. So to calibrate a projection setup, you really NEED to be reading off the screen. If your meter isn't suited to that use, sell it and get a different meter that is more appropriate for projectors. If you sit 10 feet from the screen and the meter you use has to be 1 or 2 feet from the screen, the meter will be positioned correctly if blocks your view of the center of the screen when you are in the main seat. But that sort of placement is where you get into trouble with the shadow of the meter. The farther you can place the meter from the screen without "reading" beyond the edges of the screen, the better for calibration off the screen.
"Movies is magic..." Van Dyke Parks
THX Certified Professional Video Calibration
Widescreen Review -- Home Theater & Sound