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Old 04-18-2008   #31
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Default Re: Proper screen size for best quality picture

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Originally Posted by Gerben Van Duyl View Post
Hi,

The optimal screen size (horizontal image) is Seat Distance / 1.2. Meaning that if you sit 10 feet away from the screen, the screen should be 8.33' wide. This is because this is exactly 45 degrees to the Left and Right edge of the screen, which is also where the speakers should be, behind an acoustic transparent screen. All per THX cinema specs. Of course your room needs to be dark without any reflective surfaces or objects.
Using this formula, I would need an 180 in. diagonal screen! Not going to happen for me.
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Old 04-18-2008   #32
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Default Re: Proper screen size for best quality picture

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Using this formula, I would need an 180 in. diagonal screen! Not going to happen for me.
I understand. How close can you get to that size? These recommended sizes are indicated by the behaviour of audio in the room, which establishes a sweet spot. It also is standardised by THX Cinema standards, which give us these screen sizes, based of viewing angles and audio angles to the L and R side of the screen and the speakers. Of course you can have any size screen you like, these recommendation give you a screen with the same viewing angles as from the mixing position in the dubbing stage, where the film is made.

Regards, Gerben.
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Old 04-28-2008   #33
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Default Re: Proper screen size for best quality picture

I was reading some reviews on projectors & the Lumens output were between 1000 & 1500.
How do you figure out what is the ideal screen size for lumen output?
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Old 04-29-2008   #34
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Default Re: Proper screen size for best quality picture

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I was reading some reviews on projectors & the Lumens output were between 1000 & 1500.
How do you figure out what is the ideal screen size for lumen output?
The THX ciname target is 16 foot-Lambert (ft-L), reflected of the screen(!), which is:

foot-lambert n. An obsolescent unit of luminance equal to that of a surface emitting or reflecting one lumen per square foot, a completely reflecting surface illuminated by 1 foot-candle having a luminance of 1 foot-lambert.

So, per 1,000 lumen, you can correctly illuminate 1,000/16 = 62.5 square feet of screen surface, ASSUMING perfect luminance (reflection) of the screen. Considering a gain of say 0.97 of a typical 'neutral gain' screen, the 16 ft-L would become 15.52 ft-L, which is still twice as good as most neighbourhood cinemas.

So, if you are looking at installing a 10' screen with a 16:9 ratio and 0.97 gain, you have 56 square feet of screen surface, requiring 56 / 0.97 * 16 = 923 lumens of output from the projector.

Next question, can you trust the lumens specifications from the projector manufacturer? Bottom line, you need to measure this, using appropriate equipment. A good AV dealer / installer can do this for you.

G.
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