Originally Posted by Geof
I'm not sure I follow. All JVC's achieve max on/off with the lens set for max distance, min iris, and low lamp....if one needs to use minimun iris (ie, wide open) then contrast takes a huge nosedive from the published specs. In this case I think these viewers will really see the benefit of a DI.....as the DI will help restore some of the black level capability that cannot be achieved when the projector is operated for "max brightness". Now for some (like Manni) who have the iris fully closed and at a mid throw he is already seeing most of the advertised On/off.....the DI will improve this considerably but I don't think it'll be as obvious as what will be seen for those whose need to operate with more lumen output (ie, at lower native on/off). I certainly could be wrong though.....
I suspect the DI will be located after the panels, and after the image forming wire grid polarizer....
Yes, but the iris is not static, it's dynamic.
If we use these numbers for simplicity:
Fully closed iris native contrast. 100K:1, brightness 100 lumens
Fully opened iris native contrast 30K:1, brightness 1000 lumens.
This would mean that if the iris was run in dynamic mode the native contrast in dark scenes would be close to 100k;1 and bright scenes 10k:1. However, the total dynamic contrast would be = white level in bright scene/black level in dark scene = 1000 lumens/(100 lumens/100.000) = 1 million:1. AND you would get this dynamic contrast and still get 1000 lumens! The iris opens up in bright scenes remember.
So you wouldn't choose to which degree you would have the iris closed like in todays JVC. It's dynamic and changing from scene to scene. The only settings you're selecting that's affecting contrast and brightness is the tele-zoom.
However, if the lamp is not in the lens but in front of the lamp, closing the dynamic iris would not affect the native contrast only the brightness. Then you could have a situation with a second iris in the lens that can be set independently from the dynamic iris that will affect both brightness and contrast ratio. This is not the way Sony make their projectors. They only have the lens iris that can work either in dynamic mode or in a fixed setting (which would affect CR).