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Old February 22nd, 2010, 12:43 AM   #1
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Is this a rear screen projection presentation?

Ok, so this is still distribution, just for a large audience....

Most presentations I see are done with a small projector up on a lame slide up silver screen on an easel...and the speaker has to avoid walking in front of the light beam.

So if you want to be able to see the screen well, the speaker is dark, if you illuminate the speaker, the screen gets washed out...

So these large audience presentations done by Steve Jobs, any idea on how is the projection done on the screen in this video?

Steve Jobs Apple Keynote Presentation
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Old February 22nd, 2010, 01:01 AM   #2
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yes it is probably a rear projection, there is also the hanging projector too though, where it hangs up high and projects down. they can even have pretty steep angles going with the high hanging projectors.
they use hanging ones on the stages sometimes, as long as the people on the stage stay about 3feet from the screen they dont get in the projection.
most projectors will do rear projection, you just hang what looks like a white bed sheet type scrim thing. then the projector has Inversion setting to invert the picture. Problem with rear projection is you have to have some Distance Behind the screen. where i have seen them used they wasted a LOT of floor space behind the screen closing up the room we were in.
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Old February 23rd, 2010, 06:15 PM   #3
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Is the material it projects against expensive or specialized?
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Old February 24th, 2010, 01:55 AM   #4
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honestly you can use a bed sheet of the right thread count :-)
For Older big screen televisions they used what looked like plastic difussion, something that the light hits instead of goes right through, and that allows as much light to pass through as possible. So thin but without holes or mesh. the least ammount of blocking, with still the light strike point instead of passthrough.
the people doing portable setups are usually using Cloth like materials , because it doesnt have wrinkels after setup.
Projection Material

also the perfect shower curtian will probably work, if you want to save $150 :-)
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Old February 24th, 2010, 04:51 AM   #5
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Dave,
the last 4 or 5 seminars I've done entailed rear projection (actually very common for larger seminars and conventions) and while Marty is right that it can be space wasteful depending on the projectors used you can get a short throw lens that will cut down tremendously the amount of room needed for the projector. Of course they aren't the little portables you get at Bestbuy, these are generally very large units and on the shows where we use them, we usually try to put them on scaffolding instead of hanging them only because some of the venues either have a very high ceiling and it wasn't practical or there was really no where to hang the projectors from and while you can use materials other than a rear projection screen when working on a 3 day show where the client has paid say 10 to 25K for gear rental and crew they don't want to see bedsheets hanging they want to see those nice big 14X10 fastfold screens with nice pipe and drape on either side and a bottom skirt as well as a top valance. Maybe some won't say anything but the people I've done the work for well, they would. I"m just sayin'.
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Old February 24th, 2010, 11:23 AM   #6
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Rear projection indeed does better at not washing out when lights are mis-aimed. The reason is that most light is transmitted instead of reflected.

Front projection is brighter and higher perceived resolution, in general, though, resolution rarely comes up as a problem with RP. And, a brighter projector would be speced for RP.

Either may be used, depending on a bunch of factors. For either, the key is good lighting. There are reasons why there are professional specialties in these areas. Many techniques for dealing with the specialized problems that occur.

Fly of equipment should not be done by inexperienced technicians. Some venues will only allow certified riggers to fly, in consultation with venue engineers so as to stay within safety limits of the hang-points ("picks").

Ground support (scaffolding, etc.) can be set without rigging training, one doesn't have to wait for the scissor lift or the rigger for setup or strike - generally, ground support is used whenever possible.
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Old February 24th, 2010, 11:34 PM   #7
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so would you say generally speaking that there will be MORE light from the projection with a good rear projection screen or from a super glass beaded wizz bang front projector that is more reflective, meaning it has a lesser viewing angle at high brightness?
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Old February 25th, 2010, 02:33 AM   #8
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I see a couple of sources for different grades of 12' x 9' rear projection plastic material, but the jury is still out how it would be set up as far as an inexpensive portable frame with valances, etc.

The organization that is having me do a presentation has pretty much no budget. Even a 1920 x 1080 projector will be like pulling teeth. I just want to do something a little more polished, and their lame roller reefing projector screen on a tripod is, well, lame looking, and so is the speaker roaming the room front avoiding the projector light that is illuminating dust floating about, and I have never seen the venue with a means to elevate the projector.
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Old February 25th, 2010, 05:45 AM   #9
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Dave,
It sounds like by the time you were to buy some material and then jerryrig a way to make it work you might be able to rent a fastfold screen and perhaps a projector. I would start calling rental houses in you area, I'm sure there are a couple. As for raising the projector again IMO the best way is to use scaffolding and would likely be something a rental hous would have. I realize ther is little or no budget (there never seems to be no matter who the client is) but there are somethings that just require money and without it the presantation just doesn't go off as well as it could.
If it were me, I'd make some calls, get some pricing and present to the client as an option and explain why it's the right thing to do. they may not but at least you'd be able to say you tried.
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Old February 25th, 2010, 01:24 PM   #10
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Quote:
Originally Posted by Marty Welk View Post
so would you say generally speaking that there will be MORE light from the projection with a good rear projection screen or from a super glass beaded wizz bang front projector that is more reflective, meaning it has a lesser viewing angle at high brightness?
Hmm... Somewhere here I have a book that discusses this in detail, but haven't seen it in a few years.

If you look on the manufacturer's websites, you'll find "gain" information for various screen surfaces. If we assume a given projector's brightness, RP will lose some light, something like 35%. FP on a matte screen will be our standard at 100%. Glass beaded and silver lenticular gain some reflectivity over matte, at the sacrifice of viewing angle, as you noted.

However, when we go into the av rental market, we'll find that all the front surfaces are matte white - they don't want to deal with gain vs. narrower viewing angle, they'd rather rent you a more expensive projector if you need more brightness. This approach works, and doesn't require laying out the projection and audience in a CAD program to determine viewing angles.

Matte has proven to be the most usable and adaptable front surface for general use, but, some permanent installations use lenticular so that the image is both brighter and isn't as washed out by ambient light.
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Old February 25th, 2010, 05:50 PM   #11
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thanks, i havent tried to go rear project myself yet. i use a screen that is NOT glass bead, but its not as flat as matte, and brightness was one of the things we specifically "bought into" to survive various locations.
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Old February 27th, 2010, 12:39 AM   #12
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I never heard of fast fold screens. The material doesn't sound like it is all that expensive, but I am wondering about the frame, who makes them and the portability of that.
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Old February 27th, 2010, 12:58 AM   #13
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I believe fast-fold was originally what Da-Lite called their frames, but, now all the major manufacturers make similar frames. Different snap patterns, though, so, surfaces/frames are not interchangeable between manufacturers.

It's basically 1-1/4" square aluminum tube, put together with hinges and latches. Larger screens use flat welded truss made of the same material, sides hinge/latch, then are screwed together with speed cranks.

9x12' is a big-ish standard size, when collapsed, it might be about 1.5'x1'x4.5'. Then, there are screw-on legs made of the same material.

These systems work pretty well, though after a few years of rental use there can be some considerable sag in the frame when the surface is stretched on it.
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Old February 27th, 2010, 02:54 AM   #14
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I had seen the Da-Lite, but I don't recall seeing any that were rear projection Fast-Folds.

Also, it it didn't seem to have any nice black border flat pieces around the perimeter....so they look sort of unpolished.

It would be fairly easy to make something about 12' x 6.75' that portable for less than $200 excluding screen, but the issue is attaching screen material with no wrinkles.
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Old February 27th, 2010, 06:54 AM   #15
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Da-Lite Deluxe Complete Screen Fast-Fold Portable Front Projection Screen - 10.6' x 14' - 211" Diagonal - Video Format (4:3 Aspect) - Cinema Vision
This is from B&H- just one of many.

Actually they have a nice black border all the way around, have draping that snaps right on, including side drapes, bottom skirts and top valance and the ones I've used over the last years have 2 screens. One is front projection and the other is for rear projection.
The fast folds can be a real pain to set up and can even be dangerous to strike but it's been my experience they are pretty much an industry standard, if not by name type.
Kinda like Kleenix. there's only one brand of kleenix but pretty much all tissue is called that no matter who manufactured it.

BTW, the screen is snapped into place and is a 2 person job. Good luck trying to make one but personally, I think you'd be better off renting or buying the real thing. They have down cold and there's a reason it's an industry standard.
Just my $.02 worth
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