How to calibrate and measure ft lamberts? - AVS Forum
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post #1 of 5 Old 03-14-2012, 01:10 AM - Thread Starter
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Aside from an isf calibration, how do I measure the correct amount of light I'm throwing? First, I have a 1.0 gain screen. What image do I project, a 100 ire full-frame white field? Then, do I get a light meter and try to get close to the 16 ft lamberts recommend?

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post #2 of 5 Old 03-14-2012, 06:29 AM
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http://www.avsforum.com/avs-vb/showthread.php?t=755705
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post #3 of 5 Old 03-14-2012, 06:39 AM
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Yep, use the instructions in the link given, or buy one of the versions of Calman or Chromapure with the i1 Display meter and the software will give you a ftL reading off your screen.

(I assumed by "aside from an ISF calibration" you meant paying someone else to come in and calibrate. )
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post #4 of 5 Old 03-14-2012, 10:35 AM
 
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If you are using a light meter than reads out in lux, just put the meter at your screen center and aim it at the projector displaying a white full screen pattern filling your screen. Take the reading, multiply it by your screen gain and divide by 10.76. Since my screen gain is 1.0, all I need do is read the meter in lux and divide by 10.76.
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post #5 of 5 Old 03-14-2012, 06:22 PM
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Quote:
Originally Posted by AV Science Sales 4 View Post

If you are using a light meter than reads out in lux, just put the meter at your screen center and aim it at the projector displaying a white full screen pattern filling your screen. Take the reading, multiply it by your screen gain and divide by 10.76. Since my screen gain is 1.0, all I need do is read the meter in lux and divide by 10.76.

Most light meters allow you to read out in lux or fc (footcandles). If you switch to read the value (measured as you describe) in fc, then the lumen output of the projector is (# of fc)x(screen area in sq ft). The ftL coming off the screen is (# of fc)x(screen gain).
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