Film-Tech Forum ARCHIVE: Measurements for Home Theatre Screens

This is topic Measurements for Home Theatre Screens in forum The Afterlife at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=12;t=000598

Posted by Monte L Fullmer (Member # 2797) on 10-17-2007, 10:27 PM:

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

Posted by Paul Mayer (Member # 355) on 10-17-2007, 11:39 PM:

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.

Posted by Monte L Fullmer (Member # 2797) on 10-18-2007, 12:28 AM:

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

Posted by Mark Gulbrandsen (Member # 72) on 10-18-2007, 06:58 AM:

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

Posted by Mitchell Dvoskin (Member # 751) on 10-18-2007, 07:56 AM:

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.

Posted by Robert Minichino (Member # 3495) on 10-18-2007, 09:23 AM:

As far as picking a screen size based on visual quality, I liked this calculator: http://www.myhometheater.homestead.com/viewingdistancecalculator.html

Posted by Monte L Fullmer (Member # 2797) on 10-19-2007, 02:07 AM:

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

Posted by Larry Myers (Member # 738) on 10-19-2007, 09:02 AM:

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.

Posted by Scott Norwood (Member # 30) on 10-19-2007, 12:17 PM:

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.

Posted by Monte L Fullmer (Member # 2797) on 10-19-2007, 01:10 PM:

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

Posted by Larry Myers (Member # 738) on 10-19-2007, 04:46 PM:

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.

Posted by Brad Miller (Member # 2) on 10-19-2007, 05:17 PM:

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]

Posted by Larry Myers (Member # 738) on 10-19-2007, 06:58 PM:

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 ]

Posted by Mark Gulbrandsen (Member # 72) on 10-19-2007, 09:08 PM:

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

Posted by Larry Myers (Member # 738) on 10-20-2007, 11:41 AM:

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.

Posted by Monte L Fullmer (Member # 2797) on 10-20-2007, 02:45 PM:

Question: noticed in some projector ads on the web, like Costco for example, of "business office" and "home theatre" projectors. What would be the difference?

-thx Monte

Posted by Larry Myers (Member # 738) on 10-20-2007, 07:09 PM:

You really need a 1080p projector and nothing less so you can upgrade to Blue Ray or HDDVD later. My projector has an automatic anamorphic sensor. It actually plays it squashed for about 1/2 second and then goes full anamorphic.

So with a 2.35 anamorphic, the image will have bars on top and botton of the screen and you need to set the zoom lens to the 8 ft wide image. This is second best resolution. If the DVD is 1.85 anamorphic, the image will spill over the top and bottom of the screen at 8 ft wide. You need to reset the zoom lens to a 3.5 by 6.5 ft wide image. This is your best resolution possible and is very close to film.

Some DVD's will just play a non-anamorphic 2.35 image in the center of the screen. If this is the case, you really need to zoom out to the max. The problem is, the image will look like crap. You must read the back of the DVD case to see if it says anamorphic 1.85 or anamorphic 2.35. Otherwise forget it. Then not all DVD's play the same. Some DVD's have heavy compression which tends to give a ghost image. To me, the best of the best DVD is Star Wars the "Revenge of the Seth". The DVD is so good that if someone offered me the film in 35mm for free and all I had to do is pay shipping, I would turn it down.

Posted by Monte L Fullmer (Member # 2797) on 10-20-2007, 11:06 PM:

Thx, Larry for your discussion and presenting various facts concerning home digital display.

Yes, on what you've covered is what is one the box, per say. "Enhanced for 16:9 TV's" meaning that they're squeezed images and the image will be expanded to fit such screens and keep the same visual quality.

Whereas, you also mentioned, the anamorphic imagery downsized in a 4;3 frame which then has to be blown up to fit the adjusted wide screen, in which in the process, the loss of visual quality.

Now, for another question, per chance: I've seen dig projectors that have dual display mode: the 4:3 and the 16:9. Then, would this projector have the availability to project these anamorphic released DVD's which, once again, are "enhanced for 16:9 displays"?

Is your unit, LCD, or DLP?

thx - Monte

Posted by Larry Myers (Member # 738) on 10-21-2007, 09:52 AM:

My projector is LCD. It's very bright in a totally dark room. My theater more or less looks like the corner neighborhood theater you went to as a kid for 25 cents in the 50's. It's a 10 by 10 room with a booth off to the back. The Walls are painted very dark gray on the bottom and dark gray on top with a institutional black strip all the way around the middle of the wall. The curtains are a mix of black and very dark red.

It's simple and cheap and has full 35mm and digital capability.

It works good enougth for me.

I had an expert in Professional Digital Theaters recommend the Panasonic unit I am using. I found a guy selling them on Ebay that lived about 30 miles from me. I went over and test the unit. Then paid him the $1000 cash and was on my way. Otherwise, I know nothing about Digital Projectors.

Posted by Mark Gulbrandsen (Member # 72) on 10-21-2007, 01:29 PM:

quote: Larry Myers
I had an expert in Professional Digital Theaters recommend the Panasonic unit I am using. I found a guy selling them on Ebay that lived about 30 miles from me. I went over and test the unit. Then paid him the $1000 cash and was on my way. Otherwise, I know nothing about Digital Projectors.

I've installed alot of the $6000.00 Panasonics in theaters for pre-show... nice images and the projector interfaces directly to relay contacts in existing automation but the lamps can be pretty darn expensive... approaching $500.00 ea. Lamp life has also been poor 250 hours at best at one site running 7 of them and there is no warranty given on video projector lamps even though they may say 2500 hours or some BS like that. The warranty is worthless. That site running 7 units is at a very high altitude.. almost 7000 feet so we have been considering outboard exhaust blowers on these in attempt to increase lamp life in spite of the blowers being set to high and also running for a while after the lamp shuts down... Other small plexes that I service have been installing small Dell projectors that cost about a grand new and they have had better lamp life nad the lamps are far less expensive, Image quality is ok on a small screen.

Mark

Posted by Monte L Fullmer (Member # 2797) on 10-21-2007, 07:57 PM:

quote: Mark Gulbrandsen
but the lamps can be pretty darn expensive... approaching $500.00 ea

..true, know how that is. We've got an 8 screener using Proximas 6800 series (2800 plus lumens, XGA LED display, 275w bulb unit) and I have to change bulbs well before their so-called warranted life.

Luckilly, we're not footing the bulb bill where the ad company is. Plus, the ad company uses reman bulbs as well.

-Monte

Posted by Larry Myers (Member # 738) on 10-22-2007, 10:51 AM:

So far so good on my 600 hours of use. The bulb is rated for about 1800 hours. I believe the type of bulb in the Panasonic I am using is several hundred dollars to replace.

Anyway you look at it, a home theater cost money. The issue I believe here is just how good do you want it and how much do you want to spend. I know of people who spend $30,000 just in drywall, paint and labor putting up a home theater. I have about $1500 in drywall and paint with my own labor. Then another $3000 in equipment for both 35mm and DVD projection capability.

This Old House Bob Velia did a special on TV about 2 million condo in downtown Boston. It had a $100,000 home theater with a powder room that used real gold plated bathroom fixtures. A very nice touch indeed.

Posted by Jack Theakston (Member # 4484) on 10-23-2007, 02:57 PM:

Let me also add that aside from the screen wall's height and width, consider the amount of films you'll be watching in each ratio. If you have a high volume of Academy Ratio films, you'll probably want to stick with a 1.37:1 screen. If most of your films are from the '50s or after, you should try to get a wide screen.

If you're going with a wide screen, I'd suggest one that is natively a 2:1 ratio. You'll be compromising both scope and flat with your masking, but it will be a better overall compromise if you're running an equal amount of both.

Posted by Frank Angel (Member # 248) on 10-30-2007, 03:57 AM:

Wouldn't you get the best image if you used the projector's native chip size, either 16:9 or even 4:3, using an anamophic DVD, leave it a compressed image and rather than stretch it digitally in the projector, use one of those 1.4x anamorphics designed specifically for video projection. I was told someplace along the line that that was the way to get the best image. Evidently in order for the projector to make image corrections digitally it has to futz with the pixals and you loose resolution. My friend insists that you shouldn't even do keystone correction in the projector; he is a fanatic and when I tried to adjust the keystone distortion with the menu, he started screaming at me to either put the projector in the right position in the middle of the screen so there is no distortion or use side masks like you do in film, but DON'T use keystone correction. Perhaps he over exagerates, but his explanation, at least as I undertood it, made sense.

Only thing is, I looked up the price for the Schneider video anamorphic lenses -- pretty much you could buy another projector at those prices.