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I just ordered a Mits HC5500 that is said to have a new faster auto-iris that improves black levels.


But does any of you guys know how an auto-iris works. How does the projector measure how much light it reflected to the screen how does the system use this information to create better blacks.


I've been looking around for an article on this but can't really find anything.


any info would be much appreciated
 

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Quote:
Originally Posted by Jens Dahl /forum/post/14279854


I just ordered a Mits HC5500 that is said to have a new faster auto-iris that improves black levels.


But does any of you guys know how an auto-iris works. How does the projector measure how much light it reflected to the screen how does the system use this information to create better blacks.


I've been looking around for an article on this but can't really find anything.


any info would be much appreciated

It is kind of like a shutter that will block the lamp output on dark scenes to get better blacks, and open up on bright scenes. On scenes with inky blacks and bright whites it will ajust a lot depending on the movement in the scene causing brightness flucuations. I have not viewed an HC5500 yet so I cannot say how "fast" it is, but from the ax200u and a few others it can be annoying.
 

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It is in German, but you can go to http://babelfish.yahoo.com/ then enter http://www.cine4home.de in the part for translating a web page, enter "German to English" and then hit the Translate button. The relevant article is the one that starts "Large know-how special".


As a simplified example, the projector is looking at the input signal and if the brightest thing in the image is half of white, then it can adjust the iris so that the amount of light is half (kind of like cutting bulb power to half) and basically double the light level at the chip/panel level for everything in the image. Video black is supposed to be zero, so it doesn't get doubled and so the chip(s)/panel(s) put out half as much black as originally, with all other levels staying about the same (since the light was cut in half for one stage, but double for another stage). In actuality it is a little more complicated than this with trying to avoid pumping in the images, avoid crushing things up near white too much, having to consider the brightest thing in any primary (red, green, and blue) and not just white/gray, and the washout effect can keep the blacks from getting much blacker if there is much bright stuff in the images, but that is the general methodology.


--Darin
 
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