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Author
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Topic: Light meters for screen levels
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 01-10-2008 07:16 AM
The problem arises that if one uses a poor quality meter that all they are provided with is a relative number for that meter rather than any sort of accurate measurement. This is equivalent to some saying..."hmmm that looks like 14fL" and carries with it no more weight.
Now, if you do have access to a calibrated meter (just for a loan) and you have a lesser meter, you can reference the lesser meter against the good one and see if it will provide reliable readings of an accuracy needed for the application. Be sure to check the lesser meter over a significant range of values likely to be encountered...say 6fL up to 30fL.
Light meters may seem stupidly expensive but in truth, they are not. There is no economy of scale in that technology. Furthermore, their value is in the quality of readings they provide. Just how many meters do you think they sell each year? The number is likely in the 100s or even 10s. For that, they had to design the thing...go through revisions to get it working, and ensure its accuracy. Then they had to go to manufacturing on a small-volume device which means all of the metal fab or molded plastic...etc also enjoys no economy of scale...finally market and package the unit. I guarantee you that NOBODY is getting rich on light meters (for cinemas at least).
Now I do agree it is expensive. In fact, it is probably the worst bang for the buck equipment in a tech's tool kit. You typically point-shoot take a reading...maybe make an adjustment and 1-2 minutes later you are done. How many billable minutes does a business have to generate before their light meter has "paid for itself?" The answer is forever...because for them to be worth using, their accuracy has to be checked annually.
Now the Ultra Stereo PSA is a bit better in many regards since it is a very useful alignment tool in addition to being 45 light meters in one box. It is more expensive than the Spectra but it is also MUCH more useful. You can get absolutely EVEN and properly lit images with it. As someone that sets up a lot of multi-projector systems, I find it to be THE best way...it sits down in the auditorium while I can adjust the systems in the booth. When done, the difference between projectors is minimized.
Now if you want to complain about the cost of meters...start pricing out chromaticity meters. They are essential for setting up DCinema and really useful for film too (particularly for multi-projectors for color balance). The average price on them is well over $10K. I'm happy to say, that USL's PSC has done well for us (even before DCinema use) but has actually done well in setting up DCinema projectors (and I've A/Bed it to much more expensive units). In one instance, I found it to be more accurate...but that was likely that ours had been freshly calibrated and the other unit had not.
Steve
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