Axiom Home Page Forums General Discussion Home Theater Screen size -- how big is too big ?

Is setting the lens to "pass through" just pushing a switch or lever to do this or is it more complicated than that. I am also confused about this point.

Just saw an artice for a Funco CineWide a couple weeks ago. It uses electronic processing to stretch the image vertically and an auxiliary anamorphic lens to stretch it horizontally. It claims that by doing this, all pixels were used to make the 2.35 image. But since this is a Runco I bet they start at about $10k. We can only hope that more companies will catch on an we could get an affordable version of this in the near future. I would also like to watch movies on a 2.35 screen when I get a projector in a few years since I mostly watch movies.

Correction: Runco not Funco

the "f" and "r" are right next to each other

On the Prismasonic lens, you have two knobs. So when you have a 2.35 movie, you just turn the knobs to stretch the right/left sides of the image horizontaly to fill the 2.35 screen. When watching a 1.85 DVD or 16:9 HD channel, you turn them back to "pass through" mode, so the image is just as if you didn't have a lens in place.

Hey Randy, your last comment made me wonder...

Does use of a 2.35:1 lens like yours reduce the brightness of the projector? I mean, I wouldn't expect it to be noticable or anything, but when you use a 2x teleconverter on a camera, the effective f-stop changes. Maybe it's a different principle.

What Randy just described seems to be one of the big attractions of the Prismasonic products. With a Panamorph lens, either vertical compression or the new horizontal expansion, you have to physically remove the lens, either with one of Panamorph's very high quality motorized transports (which cost about the same as the lens) or with a DIY-equivalent made from a couple of drawer slides and a scrap of plywood. Fortunately the alignment between lens and projector does not seem to affect image quality, although a real cheap DIY transport probably results in some image shift.

For anyone not completely sick of my own HT adventures, I have "plan B" up and running. Turns out that if you have the projector at the right height, you can get the right amount of vertical image shift "for free" when you zoom between the right settings for 2.35:1 and 16:9.

In my case I wanted the 2.35 image to be aligned at the top of the screen so that eye level would remain 1/3 of the way up from the bottom of the image. That meant the projector lens needed to be about an inch above the bottom of the 4x8 screen, or raised about 4" from its current location on the top of a picnic cooler (don't ask).

The results are great. I have to manually zoom when switching aspect ratios but no shifting required, ie other than keeping greasy fingers away from the lens the aspect ratio change can be handled by anyone. When visitors bring kids who might be watching unattended the plan is to leave the screen masks at 16:9 and live with a slightly smaller 2.35 image. This what the HT geeks call "constant width operation" and the rest of us call "stop mucking with the projector and watch the movie".

All I need now is to add some masks to the screen. I need about 7" of fixed masking above the top of the screen to handle the black bars which splash over the top when zoomed in for a 2.35 movie, a moveable 7" mask at the bottom of the screen, and 2 moveable 6" masks at the sides. I'm thinking about trying to rig a bit of a shadow box around the screen as well, which would also provide a "parking spot" and protection for the unused masks.

Here's a link to a guy who did a nice setup with fabric masks, only his system aligns the images at the bottom of the screen rather than the top. I think this was necessary because his screen is mounted higher than mine :

http://dustin.bunnyhug.net/

One note I should make re: previous posts. Earlier I said that a constant-area rig was a good alternative to a "big honkin' 2.35 screen". After some thought I have refined this -- constant area is a good alternative to a "big 2.35 screen" or a "big honkin' 16:9 screen". Jakeman runs a really big 16:9 screen in his HT and the 2.35 movies look fantastic... but then his screen is almost 10 feet wide.

>>Does use of a 2.35:1 lens like yours reduce the brightness of the projector? I mean, I wouldn't expect it to be noticable or anything, but when you use a 2x teleconverter on a camera, the effective f-stop changes. Maybe it's a different principle.

Good question. It took me a while to get my head around it... in fact after a couple of attempts I am on the verge of giving up and waiting for Randy to answer.

The short answer is "if you zoom out so the 2.35 image ends up the same width it was before you added horizontal stretch from the lens and vertical stretch from the projector/player, then the image is actually BRIGHTER than before because you are using all of the LCD panel rather than just the middle 3/4.

I imagine that if you just stick the lens in front and make the image wider then it will be less bright, exactly as you would expect.

The trick is that you do a number of other things at the same time, none of which can be done without the lens, and the result of all those actions together is a sharper, brighter 2.35 image.

EDIT -- you can tell this isn't simple -- I had to edit my own post three times before it was what I considered "readable". Hint -- if you think about a vertical compression lens rather than a horizontal expansion lens it's a bit easier to grasp, even if the trend seems to be towards horizontal expansion lenses these days.

FWIW, I think the big advantage of vertical compression lenses is that if the projector is already mounted you don't need to move it or change the zoom settings. Many projectors still don't have the 1.33 zoom range you need to compensate for the horizontal expansion, and even the ones that do are rarely mounted in a position where you have enough unused zoom range.

I do not see any reduction in the brightness of the image for any material. Actualy for 2.35 movies, the image can be upto 20% brighter. Because you are reclaiming 33% of the pixels that were taken up by the black bars, your image actualy improves and can be brighter.

I'm kind of fascinated by all of this.

John, the answer to your original inquiry is "size doesn't matter".

Also, tell me about the picnic cooler...