Quote: |
A misconception prevalent in our industry and erroneously promulgated by the author of these articles has been that double stacking projectors produces less than twice as much light. This assumption, we are now pleased to understand, is not true. 1 + 1 does = 2; every time. In an important sense, however, this lineally additive quality of lumens is true only if the device measuring them is other than the human eye. Our eyes, you see, do not respond to changes in brightness in a straight, linear fashion. Instead, they react logarithmically to changes in their input and thus, for instance, we are able to find our way out of a darkened movie theater, yet continue to see when we emerge onto the brightly lit street outside it. If we array a human audience before some screen and first illuminate it with a 1,000 lumen projector and then turn on a second 1,000 lumen projector, will the audience see twice as bright an image? No, it will not. The perceived brightness will increase only by about 50%. It will not double. |
Jerry Maxey wrote on Thu, 27 September 2007 12:03 |
Obviously, we're not talking about projectors displaying different images. I think you are promoting the very "misconception prevalent in our industry" referred to in the paper you quoted above. When the paper you, yourself quoted says "1 + 1 does = 2; every time", do you think that the author was really only talking about full white screens? |
Jerry Maxey wrote on Thu, 27 September 2007 17:20 |
First of all ANSI Lumens are not a direct measure of the light output of the projector, but rather a measure of the light reflected from the screen. From Hiretec "Choosing an LCD Projector": "ANSI lumens is an average Lumen measurement around the screen. This is accomplished by dividing the screen into 9 rectangles (three vertical coulombs and three rows). Take a measurement of light using a good spot light meter 1 foot away from the screen pointing at the center of each of the nine areas. Then you take the average of the nine areas and that is your average (ANSI) Fl (foot-Lambert) light output." |
Jerry Maxey wrote on Thu, 27 September 2007 17:20 |
From Hiretec "Choosing an LCD Projector": "ANSI lumens is an average Lumen measurement around the screen. This is accomplished by dividing the screen into 9 rectangles (three vertical coulombs and three rows). Take a measurement of light using a good spot light meter 1 foot away from the screen pointing at the center of each of the nine areas. Then you take the average of the nine areas and that is your average (ANSI) Fl (foot-Lambert) light output." |
Jerry Maxey wrote on Thu, 27 September 2007 12:03 |
Obviously, we're not talking about projectors displaying different images. I think you are promoting the very "misconception prevalent in our industry" referred to in the paper you quoted above. When the paper you, yourself quoted says "1 + 1 does = 2; every time", do you think that the author was really only talking about full white screens? |