Quote:
Originally Posted by SirMaster
So he is using an anamorphic lens. The lens stretches the image out horizontally to fill out the screen. It's a rather large 15ft wide screen.
The projector is doing the vertical stretch. We don't use madvR to do the stretch for other reasons. (rendering times go from 30ms to 300ms when we enable anamorphic stretch in madVR due to how the image and chroma scaling compound or something like that.)
His screen is 2.37:1 and the movie is 2.40:1.
What he normally does, is zooms the projector so that the narrowest movies (2.40:1) fill the screen vertically, and then that means they overshoot the sides by a bit. This also means that 2.35:1 movies will overshoot all 4 sides. Normally with a decent projector this isn't a problem since they offer image masking, and you just mask off the 4 sides of the projector's image to fit your screen perfectly. This is what he did on his previous JVC RS600.
However, he just got a BenQ LK970 laser projector that does not have this masking option.
I think another issue is that his anamorphic lens is not perfect and it stretches the image horizontally slightly more than it should. So the issue is that if he wants to fill his screen vertically, the image will always overshoot his screen horizontally. This is why we need to cover some of the projector's image with black essentially so that the overshoot is invisible.
I am trying to understand your edited response, but I will have to think about it some more. Maybe my latest reply here sheds some more light on the set up and what we are trying to achieve.
Recap:
2.40 movie, stretched vertically by the projector to fill the projector's full 16:9 panel. Projector stretch is a 2.35:1 -> 16:9 stretch, so there is still a small black edge on the top and bottom of the projector's 16:9 panel after it vertically stretches 2.35:1 -> 16:9, because the movie is 2.40:1.
Projector is lens zoomed to make the 2.40:1 image fill the 2.37:1 screen vertically. This leaves a horizontal picture overshoot due to 2 factors. 1, because 2.40:1 is a wider aspect ratio than his screen, and 2, because his anamorphic horizontal stretch lens is not perfect and stretches the image slightly too far.
What we need to do in some way is to take a 2.40:1 movie and essentially crop off the sides a bit to make it a narrower aspect ratio. In truth we would also probably crop the top and bottom a little bit too, but again this is a crop that really is just trimming off some of the image data turning it into black, hopefully no zooming or scaling should be taking place or else that just messes it all up again.
So if you viewed this on a normal monitor, it would look like the video does not fill all the way to the edge of the screen, but it's not shrunk so scaling is not affected, it's just covered up by black. Need to render a black border over the top of the video to cover up some of the video on the sides and a little bit on the top and bottom too ideally.
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I think you can accomplish this.
If you don't have the ability to crop an image, showing a 2.40:1 movie on a 2.35:1 or 2.37:1 screen would require leaving small black bars at the top and bottom of the image, like this, rather than have the image spill out the sides:
2.40:1 movie on 2.35:1 screen
If you define at 2.37:1 rectangle in screen config (3840 x 1620 or 4096 x 1728), then zoom control will crop all content to fit this rectangle, so it should always have the correct width and height to fit a 2.37:1 scope screen with cropping when necessary.
Under zoom control, you need to select
automatically detect hard coded black bars and
if there are big black bars ...zoom the bars away completely.
I really don't know how an anamorphic lens works in practice. So I can't tell you if the lens will stretch this rectangle correctly. You should be able to use the anamorphic stretch in madVR with zoom control enabled. If you are outputting to 4096 x 2160p, then set image upscaling to something like Lanczos3 + AR to lower rendering times for the required upscaling.
I think the anamorphic stretch looks right without screen masking in screen config with zoom control set to
automatically detect hard coded black bars and
if there are big black bars ...zoom the bars away completely.
I wrote some instructions on zoom control in the madVR guide in my signature (under 2. Processing) that could be worth reading. There are also some pictures with my TV used as the example projector screen to show what zoom control is doing, but there is no anamorphic stretch in the example. Because I can't test this, I'm not sure if I got the instructions right. I guess you can try them and report back...