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#### Westshorestudios

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If a pj is rated at, for example, 1,000 lumens (and for the sake of argument and ease of math, it really is 1,000 lumes) and it is a native 4:3 chip (either DLP or LCD), and a widescreen movie is played in proper widescreen mode (it is not stretched up to play "full screen"), how many of the 1,000 lumens are being sent to the 16:9 image on the screen?

Seems that about 30-40% of the light that is capable of being output is being "blocked" within the pj to create the black / gray bars on top and bottom of the image so that it is displayed widescreen?

Therefore, a 1,000 lumen 4:3 chip pj would be comparable, to a 600 - 700 lumen native 16:9 chip pj, right?

#### htpcfan

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True for bulb projectors, for CRTs it is slightly more complicated.

#### Erik Garci

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Quote:
 Originally Posted by Westshorestudios Therefore, a 1,000 lumen 4:3 chip pj would be comparable, to a 600 - 700 lumen native 16:9 chip pj, right?
750 lumens to be exact.

4:3 is equivalent to 16:12. So a 16:9 image within 16:12 uses 9/12ths of the height and thus 75% of the lumens.

#### Hughman

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Quote:
 Originally Posted by Westshorestudios If a pj is rated at, for example, 1,000 lumens (and for the sake of argument and ease of math, it really is 1,000 lumes) and it is a native 4:3 chip (either DLP or LCD), and a widescreen movie is played in proper widescreen mode (it is not stretched up to play "full screen"), how many of the 1,000 lumens are being sent to the 16:9 image on the screen?
As stated, though there are less available lumens in this scenerio, both modes will produce equivalent foot lamberts at the screen. Perphaps that goes without saying, I just don't know anymore.

#### Westshorestudios

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Thanks for all for chiming in.

Hugh2 - I'm not sure I understand why foot lamberts at the screen is the same?

And I assume it is just foot lamberts at the screen that we care about (when we're talking lumens), right?

#### Hughman

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Quote:
 Originally Posted by Westshorestudios Thanks for all for chiming in. Hugh2 - I'm not sure I understand why foot lamberts at the screen is the same? And I assume it is just foot lamberts at the screen that we care about (when we're talking lumens), right?
Foot lamberts is lumens/square foot so in your example the screen area is being reduced by same the relative amount as lumen output therefore foot lamberts shouldn't change.

That's right, obtaining some target of foot lamberts is generally the end goal, go too high and eye strain and or video noise becomes a problem, too low and the image may appear unrealistically dim. In this regard it is necceary to pair the lumen output of the pj with a properly sized and gained screen.

#### Westshorestudios

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That helps. Thanks.

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