How to calibrate a front projector - AVS Forum
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post #1 of 10 Old 08-30-2007, 12:10 PM - Thread Starter
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I am going to buy eyeonedisplay calorimeter to calibrate my projector. Where do you put the calorimeter? Do you put it on the screen? How would one do that? What kind of software I should use with the calorimeter?

thanks in advance
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post #2 of 10 Old 08-30-2007, 12:40 PM
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Start reading here:http://www.avsforum.com/avs-vb/showthread.php?t=737550
I would suggest getting the eye-one LT - because it is cheaper than the display 2 and you should use either Cal Man software or HCFR. The software that comes with the eyeone probes is not as good for this application. I would also recommend using the getgray dvd. Keep in mind that these are quick and dirty answers to your fairly general questions. Keep asking them.

-Greg
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post #3 of 10 Old 08-30-2007, 12:46 PM
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Quote:


Where do you put the calorimeter?

Most of the time people mount it to a tripod and angle it up towards the screen - about 3 to 4 inches away. Be careful not to measure the shadow.

-Greg
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post #4 of 10 Old 08-30-2007, 04:15 PM - Thread Starter
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Quote:
Originally Posted by angryht View Post

Most of the time people mount it to a tripod and angle it up towards the screen - about 3 to 4 inches away. Be careful not to measure the shadow.

So the calorimeter does not need to be placed right up against the screen?
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post #5 of 10 Old 08-30-2007, 06:35 PM
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Quote:


So the calorimeter does not need to be placed right up against the screen?

Well, no. Actually, there are two ways to do it with a FP: 1. Aim the probe towards the projector. or 2. Aim it towards the screen. The trick is that when you aim it at the screen, you need to make sure that you are not just aiming at the shadow made by the probe. Most people have their projector mounted on the ceiling. That means that the probe is usually on a tripod aimed upwards at about a 45 degree angle at the screen. So, I guess it is right up against the screen but with enough space to read the light not the shadow. Does that make sense? What type of FP do you have?

-Greg
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post #6 of 10 Old 08-31-2007, 10:02 AM
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Quote:
Originally Posted by rotelmania View Post

So the calorimeter does not need to be placed right up against the screen?

With a front projector setup, the screen is reflecting the light from the projector back to the viewing area. This is different than most television displays (either flat panel or rear projection) where the light source is behind the screen. As angryht notes, you can either measure the light source directly, or the reflections off the screen. You can't measure the screen itself directly.
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post #7 of 10 Old 09-01-2007, 09:01 AM
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Quote:
Originally Posted by angryht View Post

Well, no. Actually, there are two ways to do it with a FP: 1. Aim the probe towards the projector. or 2. Aim it towards the screen. The trick is that when you aim it at the screen, you need to make sure that you are not just aiming at the shadow made by the probe. Most people have their projector mounted on the ceiling. That means that the probe is usually on a tripod aimed upwards at about a 45 degree angle at the screen. So, I guess it is right up against the screen but with enough space to read the light not the shadow. Does that make sense? What type of FP do you have?

As the screen does have an effect on the color, to get an accurate measurement you need to either use method 2, OR determine an offset (in terms of x and y) between methods 1 & 2 and apply that offset to method 1. The principal problem with method 2 is that very little light is reflected from the screen at the lower IREs and many colorimeters are not sensitive enough to accurately read at these very low levels (+ are very sensitive to stray light).

Dave Hancock
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post #8 of 10 Old 01-07-2013, 02:17 PM
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Just so I (and anyone else) can be clear. To get an offset adjustment would you recommend measuring about 80IRE off the screen at an angle, then rotating the sensor to be in the light path of the projector and take a measure at the same IRE. Then calculate the offset that way?
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post #9 of 10 Old 01-07-2013, 02:23 PM
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Quote:
Originally Posted by wingman1659 View Post

Just so I (and anyone else) can be clear. To get an offset adjustment would you recommend measuring about 80IRE off the screen at an angle, then rotating the sensor to be in the light path of the projector and take a measure at the same IRE. Then calculate the offset that way?

Depending on your application, if you NEED to read from the projector, you can simply create a profile in CalMAN 5 using the same meter with the reference readings being from the screen and the target measurements being from the lens.

I would read directly from the screen unless your meter is not sensitive enough to read low light.

Joel Barsotti
SpectraCal
CalMAN Lead Developer
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post #10 of 10 Old 01-08-2013, 08:52 AM
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The screen is part of the system. Aiming at the projector will not give you an accurate calibration
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