Hi, I have been thinking about a software based projector iris for a HTPC that would decrease the brightness level only on bright scenes. The idea is for projectors that use an auto iris done by hardware wich works really well to give dark scenes that ultra black feeling to the image but on bright scenes the iris actually doesn't change the brightness level at all resulting in a picture that is a bit washed out. Does anybody know of a way to decrease the brightness level only on bright scenes?
The picture being washed out during bright scenes is probably caused by the room having white walls/roof, and this causes the reflected light from the screen to bounce back from the walls onto the screen and wash out the blacks amid blended scenes. The most ideal approach to settle that is to cover the dividers and roof in dark velvet or comparative. If you can't do that, use a grey screen as that will help reduce the amount of light that reflects off of it, and retains more intra image contrast.
Including a Neutral Density filter will reduce the overall image picture shine and enhance dark levels in the meantime. What you're proposing is like a dynamic iris without any gamma adjustments so may not work that well. Some displays have a dynamic contrast facility but they don't usually work that well either
Ideally you need a reference white level of around 14fL so the image never looks too bright, but unless the pj has a manual iris to adjust the lumen output, you have to rely on other methods, such as how much zoom you use (and whee you place the pj) or if you use a filter. You should have the capacity to gauge the light yield with a meter to perceive how brilliant the picture is so you can get the reference level of reflectance.