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Topic: Making screen at home?
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John Whittle
Jedi Master Film Handler
Posts: 791
From: Northridge, CA USA
Registered: Jun 2003
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posted January 11, 2006 11:14 AM
quote:
So, if my projector Elmo ST-800 (with standard lense) will be sitting 5m from the wall, what is the biggest screen I will get both scope (2:1) and flat (4:3)?
You know, while there are mathmatical formulas which will give you screen size for any film size, distance, lens focal length, it'll only be accruate if you know the exact (to the ten thousanth) width of the projector aperture plate.
It'll be much easier for you to just set up your projector at 16 feet and measure the screen with for your standard lens. You can do the same with your anamorphic, but remember that a 2x anamorphic doesn't give you a 2:1 picture but a picture that is twice as wide (2.66:1).
Screen brightness is another matter and your scope picture will be much dimmer since you're spreading the same amount of light over twice the area.
You should also try to get your projectors closer together, at six feet there is going to be a major focus problem along with keystoning. With 8mm you can easily get the machines less than a foot apart, set one machine on a box so it's 12 inches or so above the other machine and behind it and you'll minimize keystone offset.
John
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Steve Klare
Film Guy
Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003
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posted January 11, 2006 12:14 PM
I often operate two projectors side by side and because they are on the left edge of a dining room table, I've developed an odd stoop to reach over the left-side projector to operate the right-side one. Let's hope it's not permanent!
I operate an ST-800 at about 20-25 feet from a 52" by 92" matte screen. There is brightness to spare and since I am only in the middle of the zoom range, I'm sure I could go bigger. Sharpness is fine as well.
With the same set-up and anamorphic lens, I have to zoom the projector all the way out to get the image within my 92" screen width. Brightness and sharpness are still very good. The bad part is since I am zoomed full, I can't back the projector up any more or the image will spill off the screen sides. My screen is the largest one I could permanently install hanging behind the living room curtains, so going to a bigger screen is not my first choice. (...this goes double for my wife!)
If you continue backwards from the projector, there are a pair of sliding doors and then our back porch. If I'm willing to stay with 4:3 films, I can put the projector out there and use the porch as kind of a ready made projection booth. I can't do this in 'scope unless I use a longer projection lens.
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All I ask is a wide screen and a projector to light her by...
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Winbert Hutahaean
Film God
Posts: 5468
From: Nouméa, New Caledonia
Registered: Jun 2003
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posted January 11, 2006 02:54 PM
Thanks for all inputs,
I, however, still have romantic feeling with the real theatre (an old theathre, not the cineplex) where we were amazed with the big picture on the screen, when entering the theathre.
So is there anyhow a specialised lense made for zooming the picture double from the standard lense? (or this is the reason why people change the 1.0 lense?). Therefore with a short distance between the projector and the screen we can get a really big picture.
Of course if there is a such zooming lense, I will face a problem with dimmer brightness....but I probably can change the bulb to be 200w, 24v , can't I?
help...help..,
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Winbert
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Steve Klare
Film Guy
Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003
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posted January 11, 2006 03:57 PM
Well Winbert,
Regardless of the optical limits, you will eventually run into the physical limitations of the room as well. I project in a room with an 8 foot ceiling, so I'll never be able to show academy format films more than 11 feet wide no matter what kind of equipment I'm using. Besides, nobody wants to sit in the front seats at the theater, so having an image too big at home is exactly the same thing due to the shorter distance between the screen and audience.
I had some doubts that my EFP lamped projectors could handle a 4.5 by 9 foot matte screen (the old myth that Super-8 couldn't manage an image larger than 3 feet by 4 feet was certainly there too!) What I did was experiment with my small tripod screen by setting it up where the new screen would go, then projecting an image as large as the new screen would allow. I then moved the screen around and checked the brightness and sharpness of the image. By this I was able to confidently buy a larger screen, and choose matte over glass beaded without worrying about the difference in brightness.
Maybe you can do this kind of experiment and see what works in your environment.
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All I ask is a wide screen and a projector to light her by...
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). To save the cost, I am not going to order a dedicated screen but instead painting the wall with the white paint.
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