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Author Topic: Measurements for Home Theatre Screens
Monte L Fullmer
Film God

Posts: 8301
From: Nampa, Idaho, USA
Registered: Nov 2004


 - posted 10-17-2007 10:27 PM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
I need a little help here on this topic: I'm preparing on including a home theatre unit to our family room in our home and wondering on how to measure a screen need for the throw.

Granted, the digital units gives out numerous diagonal readings per length of throw on the box that the unit comes in, but would like to possibly get the formula to figure width and height since what we basically have is a right angle triangle with the hypotenuse (diagonal) already listed on the box.

For home theatre screens listed on some catalog store locations, shows only diagonal screen sizes in both 4.3 (1.33/1) and in 16.9 (1.78/1) ratios.

If a 4.3 screen is used, then I'd have to figure in a common width screen to show widescreen presentations, and if I used a 16.9 screen, then a common height screen would be needed and the 4.3 showings would be like showing a flat movie on a scope screen with no adjustable side maskings.

This is where my lack of geometry education becomes exposed and with the one figure (let's say 93inches diagonal), what would be the formula to render the answers for the catheti, or the two legs of the triangle - since I'm measuring the outside length of the triangle, not the inside area.

Thx all for the help rendered. - Monte

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Paul Mayer
Oh get out of it Melvin, before it pulls you under!

Posts: 3835
From: Albuquerque, NM
Registered: Feb 2000


 - posted 10-17-2007 11:39 PM      Profile for Paul Mayer   Author's Homepage   Email Paul Mayer   Send New Private Message       Edit/Delete Post 
For 4:3 screens the hypotenuse is 5 (a Pythagorean triple). So if you know the screen diagonal, divide it by 5, then multiply that result by 4 for the width, or by 3 for the height.

16:9 gets a little uglier. The hypotenuse works out to approx 18.36, the square root of 337 ( 9^2 + 16^2 = 337 ). Same process applies though, divide the diagonal by 18.36, then multiply that result by 16 for the width, or by 9 for the height.

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Monte L Fullmer
Film God

Posts: 8301
From: Nampa, Idaho, USA
Registered: Nov 2004


 - posted 10-18-2007 12:28 AM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
Hey Paul -

Thx a bunch for your help and your time on your work to produce this formula for me.

The results, in using this formula for what screen size I need, really works out very well.

-Monte

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16139
From: Bountiful, Utah
Registered: Jun 99


 - posted 10-18-2007 06:58 AM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
if you have the room to fit in a 16X9 screen thats the same height as the 4X3 screen would be then by all means do so. There will be more and more 16X9 programming on TV and with HD-DVD's the 16X9 format can be used to advantage and scope pictures will be xonsiderably larger than if a 4X3 screen is used. Older stuff will of course be shown 4X3 on the 16X9 screen though. If you can afford to or rig up a movable mask system for 4X3 then all the better. Or you could blow the 4X3 up to 16X9 nd watch it that way which I understand is Joe's favorite way of watching 4X3 stuff.

Mark

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Mitchell Dvoskin
Phenomenal Film Handler

Posts: 1828
From: West Milford, NJ, USA
Registered: Jan 2001


 - posted 10-18-2007 07:56 AM      Profile for Mitchell Dvoskin   Email Mitchell Dvoskin   Send New Private Message       Edit/Delete Post 
Projector Central has an interactive projector/distance/screensize calculator at this link. Since most consumer front video projectors do not have interchangeable lenes, every projector is unique in the range (zoom min to max) at a given distance.

The link above allows you to select a projector and model, and it then gives you an interactive screen where you can adjust the distance or the screen size and it will tell you the distance range the projector must be placed in.

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Robert Minichino
Master Film Handler

Posts: 350
From: Haskell, NJ, USA
Registered: Dec 2005


 - posted 10-18-2007 09:23 AM      Profile for Robert Minichino   Author's Homepage   Email Robert Minichino   Send New Private Message       Edit/Delete Post 
As far as picking a screen size based on visual quality, I liked this calculator: http://www.myhometheater.homestead.com/viewingdistancecalculator.html

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Monte L Fullmer
Film God

Posts: 8301
From: Nampa, Idaho, USA
Registered: Nov 2004


 - posted 10-19-2007 02:07 AM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
Wow! Both sites listed above are fantastic! I do thank all of you for your comments and recommendations to aide me on this upcoming project that I'm preparing.

THX! - Monte

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Larry Myers
Master Film Handler

Posts: 371
From: Herndon, VA, USA
Registered: Jan 2001


 - posted 10-19-2007 09:02 AM      Profile for Larry Myers         Edit/Delete Post 
My home theater is rather small at 10 ft by 10 ft. Although, it contains a booth attached to the back of the room. This means the the projector is actually about 13 ft from the screen in it's own booth. One row a seats are exactly 10 ft from the screen against the back wall of the theater. The screen is a 4 by 8 drywall board with a slight curve on it sitting on stilts. About 3 inches of the top and bottom of the screen is painted black. The rest of the screen is painted the Whitest White I could find.

So the screen is 3.5 ft by 8. The sides are masked by a black curtain that varies with a flat or scope image. The Viewers are about 2.8 times back from screen height. So my screen height is always 3.5 ft high viewed at 10 ft regardless of a flat or scope image.

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Scott Norwood
Film God

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From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99


 - posted 10-19-2007 12:17 PM      Profile for Scott Norwood   Author's Homepage   Email Scott Norwood   Send New Private Message       Edit/Delete Post 
If I were doing this, I would set up the projector such that, at the longest focal length setting, the 4x3 image filled the height of the screen. This would allow zooming out for a common height image for 4x3 and wider. Most of the small video projectors don't have sufficient zoom range to do common height for 4x3 through 2.35, unfortunately, which means that you would probably be stuck with a screen no wider than 1.85 or so, and will have to live with a slightly shorter image for scope.

Some video projectors have a mode (called variously "real," "standard," and other names) that will display a 4x3 image within the 16x9 space. This can be convenient when switching formats within a program (e.g. a 4x3 short before a 16x9 feature), but isn't useful for regular 4x3 viewing, since this setting scales down the 4x3 image, giving it far less resolution than the full 4x3 image.

A cheap masking system can be constructed with black foam core side panels and velcro strips above and below the screen to hold the foam core panels in place. Foam core can be purchased from stores that sell picture framing supplies.

Regarding screens: be careful with perforated screens and LCD (and even some DLP) projectors; you can get nasty moire patterns at some distances. A microperf or non-perf screen would be a better choice.

I have a classroom-type "Da Lite" matte-white solid screen that is 84x84"; it is freestanding and seamless and looks great with 16mm and 35mm film (I don't have a video projector yet). I asked them about getting a perforated version made, but microperf screens require support on all sides and regular perfs are too visible in small venues, so I gave up on that idea.

If you want a painted screen, Markertek sells something called "screen goo"--this is expensive paint that supposedly gives a better image than regular white paint. I have never seen it and can't comment, but it might be worth checking out.

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Monte L Fullmer
Film God

Posts: 8301
From: Nampa, Idaho, USA
Registered: Nov 2004


 - posted 10-19-2007 01:10 PM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
quote: Larry Myers
The rest of the screen is painted the Whitest White I could find. ...
I've heard of some Drive-In's that would use white reflective street paint when repainting their screens - wonder if this would work great as well for your screen - to get the increase of gain instead of being matte white.


For basically, that is was is needed for digital anywhos, is a high gain (glass beaded) screen.

3.5 by 8 = 2.29/1 .. close to true scope.

Scott, I fully agree on watching out for perf screens for that is what my friend has for his home theatre (which is actually very well laid out..) - that he used an actual piece of silver screen with standard perfs. Luckilly, if you sit back far enough, it's not too noticable, but more up close ... try to ignore the holes..

Once again, Thx all - Monte

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Larry Myers
Master Film Handler

Posts: 371
From: Herndon, VA, USA
Registered: Jan 2001


 - posted 10-19-2007 04:46 PM      Profile for Larry Myers         Edit/Delete Post 
Actually I have a Devry XD with a SuperCinelux compact anamorphic with a Panasonic PT-AX100U in front of that just under the lens. It a true 1080P projector I pickup used for $1000 from a company that runs events. It had about 400 hours on it and was used in just one or two events. I have put another 200 hours on it and it still works great and very bright.

In some scenes, it's almost as good as film. Usually closeup face scenes are best and in some cases, look better then film. Busy street scenes are not so good. I believe they have too much compression. Film is hands down better for street scenes.

I actually did a test running both the film projector and the DVD projector in sync with the same movie. Taking a blocking card in front of each lens going back and forth and even overlapping like a two projector stereo setup, it's surprising how close they are.

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Brad Miller
Administrator

Posts: 17668
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 10-19-2007 05:17 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
I swear Larry, you have GOT to get rid of that Devry if you are going to do any real and fair comparisons. [Roll Eyes]

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Larry Myers
Master Film Handler

Posts: 371
From: Herndon, VA, USA
Registered: Jan 2001


 - posted 10-19-2007 06:58 PM      Profile for Larry Myers         Edit/Delete Post 
Brad your right. I do get a very crappy image through that modern $1400 SuperCinelux Compact Anamorphic lens of mine. Then the Super Simplex movement in the Devry also doesn't help much even though it has less then 100 hours logged. So it is what it is.

The bottom line. With my very bad eyesight and very poor equipment like what most people have, I really can't tell the difference. That my friend, is the center of the problem.

[ 10-19-2007, 09:00 PM: Message edited by: Larry Myers ]

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Mark Gulbrandsen
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Posts: 16139
From: Bountiful, Utah
Registered: Jun 99


 - posted 10-19-2007 09:08 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
I'll tell you one thing Larry... I'll put a modified Super Simplex up any day against one of Brad's Kinotons for overall quality of picture... definately not light efficiency though. The Super and E-7 movement parts are among some of the very best and most accurate stars and cams ever made and Supers are VERY easy on film. But I do agree with Brad that the DeVry should go ... its just not as kind to film as a Super is with all the added bells and whistles.

Mark

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Larry Myers
Master Film Handler

Posts: 371
From: Herndon, VA, USA
Registered: Jan 2001


 - posted 10-20-2007 11:41 AM      Profile for Larry Myers         Edit/Delete Post 
I have yet to add a Blue Ray system to the Digital Projector. Maybe I will have one by Christmas. Right now for me anyway, with some of the best of the best DVD's, 480p does a fine job in filling my 3.5x8 ft screen viewed at 10 ft away.

Trying to get the 5.1 sound correct has been a challenge with a 10 by 10 ft room.

One interesting thing is the film Troy. It actually looks better by DVD. I most likely have a crappy film print.

The film I did the comparison on was "The Patriot" Color balance was better on the DVD. Resolution in the beginning shots was slightly better in film. Although, when the film got to the grave stone of Benjamin Martin's (Col Francis Marion's) wife, the stone was clearly readable and looked the same with both 35mm film and 480P DVD on that 3.5by 8ft screen viewed at 10 ft.

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