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I found this interesting article on the Lumen and I thought i'd pass it on.


I found this part especially interesting...


"However, our eyes do not respond in a linear fashion to increased light output. For example, if light output increases by a factor of 10, our eyes do not perceive a ten-fold increase in brightness. In fact the human eye senses changes in light output on a logarithmic scale, which allows our eyes to be sensitive over an extremely wide range of light levels. This fact makes the minor differences in projector light output arguably negligible. If you double the number of lumen, then the subjective perception will be that the "whites" get 25% brighter."
http://www.tfwm.com/twm/articles/video/0300_Barlow.html


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James' DIY Speakers
 

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It pretty consistant with what I have seen. I have a 2500 lumen XP21N and an 800 lumen LT150. Eventhough the lumen rating is 300% more, I thought it looked roughly 50% brighter. The XP21N holds up noticably better in ambient light though.
 

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This fits well with what I observed the other day. I looked at a Sanyo XP21 and PLV-60 side by side. The XP21 is 2x brighter (2500 lumens vs. 1200 lumens), but since I was looking at a 16x9 DVD source and I had adjusted both images to be the same size, the brightness difference should be 1.56x. (This is the proper adjustment to make for different screen sizes when comparing 4:3 and 16:9 if you mainly intend to view 16:9 sources.) The projectors weren't calibrated, but both were set for factory brightness and contrast.


This brightness difference was only slightly noticable in video, and then only in bright parts, and did not sway my overall assessment that the PLV-60 had a better image (seemed to have more detail overall). Further, this held true both with the room lights on and off. I think lumens are overrated as a metric for home theater projectors, relative to things like contrast, screen door, etc. In fact these 2 projectors would be equally watchable in ambient light.



On the other hand, for computer sources (e.g. the windows desktop), the additional brightness was much more noticable.


[This message has been edited by ciamac (edited 09-26-2001).]


[This message has been edited by ciamac (edited 09-26-2001).]
 
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