Quote:
Originally Posted by gauras /forum/post/16865107
Hi Andrew,
Thanks for the clear explanations. Makes perfect sense.
The only issue would be in the ire extremes, say a dim scene with a bright red shirt
or a white sky with some black birds.
The algorithm that determines the maximum brightness / minimum brightness would
not be able to correctly work because the majority of the picture would be dark/bright
respectively. So you would see some brightness compression.
So basically if you turn auto iris on, they is no point calibrating for a custom gamma curve? I realize the hs60 does not provide a custom gamma curve, but using a radiance
with the 11 step gamma would be useless?
I have a piano 3100 and it offers a incredible 31 step gamma correction leading to
a perfect gamma curve with a ruler flat greyscale.
Unfortunately i plan to move the theater to the basement and I need some extra
brightness and lens shift capabilities and so brought the sony hs60. So I basically
calibrate for greyscale, choose a custom gamma curve and turn auto iris on for
the best picture?
I hope i see some improvement over the piano which provides a great picture.
When you start talking about specific iris implementations it gets complicated, as there are a lot of different ways to do it, and even different models of projector from the same manufacturer can have different implementations.
In theory, even if you had a scene with a very bright object on a mostly dark background, you could still use a dynamic iris to improve the contrast without any problems. (as long as the darkest object wasn't completely black, or the brightest, completely white)
The improvement to contrast might only be very minor in that situation though, which is why most projectors at least have one mode of the iris that will clip highlights/shadows somewhat to further improve perceived image contrast.
As with everything, it is a compromise.
If you want to guarantee that you'll never have any problems with brightness compression, introducing artefacts or shadow/highlight clipping, you don't use an iris.
Even if you had an iris that only opens/closes without redistributing the image brightness to compensate and improve contrast, you risk it "guessing" wrong and dimming the picture too much or making it too bright for other scenes. (without any real improvement to contrastjust brightness changes)
With some of the better iris implementations, the iris is getting to be a very transparent process now. The algorithms used are a lot more refined and they tend to avoid any distracting artefacts or "wrong guesses."
The only time I've really had an issue with my HW10 has been with white text in the middle of the screen on a full black background, or a space shot where the only bright objects are the pinpoints of light from stars. In these scenarios, the HW10 dims the image more than I would prefer.
I can't say that I've ever really noticed any brightness compression or shadow/highlight clipping, and I'd say that at least 99% of what I've displayed on my projector for the 500+ hours that I've used it has been improved by having the dynamic iris on.
I also wouldn't say there's no point in calibrating gamma, I would calibrate the projector with the dynamic iris disabled, and then turn it on afterwards. You may not be getting a perfect 2.22 (or whatever your target is) if the image is being processed to improve the contrast with the iris, but I certainly saw an improvement vs leaving the HW10 at its default gamma setting.
At the end of the day, you'll have to experiment and see whether or not the iris implementation on your projector is done well, or even if it does have some drawbacks, if the advantages outweigh the disadvantages.
As I said, I feel that the vast majority of images on my HW10 have been improved with the dynamic iris, without any real drawbacks. I can live with 1% of images potentially looking worse if 99% are improved. (or left alone if they can't be changed without it being intrusive)
I do think it's a mistake to not even try using the iris on a projector you own, simply because you don't like the idea of it changing the picture to improve contrast, or because you didn't like another manufacturer's implementation. (or an older one from the same manufacturer)
There was at least one review of the HW10 I remember reading before buying mine where the reviewer refused to use the dynamic iris, simply because they didn't like the idea of it, without actually trying it and seeing how good (in my opinion) Sony's implementation is these days. Had they used it, I think they would have been a lot more impressed with it.
