To give you an understanding of how I would specify a
projector and
screen for a project, I have a spreadsheet I use that inputs the following:
+
Image Height
+
Aspect Ratio
+ Horizontal
Screen Resolution
+
Screen Surface
Gain
+ Target Contrast Ratio (usually a minimum of 10:1 for Screen-Brightness:Ambient-Light)
+ Ambient Light (usually 2-3fc for a dark theater, 8-10fc for a classroom with the shades closed and no direct light on the
screen)
+
Throw Distance
and calculates:
+
Image Height
+
Image Area
+ Required
Luminance off of
Screen
+ Required Illuminance onto
Screen
+ Required
Projector Brightness in Lumens
+
Throw Ratio for
Lens
I've also got it factoring in handicaps such as:
+ Light Loss in
Lens
+ Light Loss due to Degradation of Lamp Over Time
There are a lot of factors and a handful of formulae that go into selecting a
screen and a
projector. It's not exactly rocket science, but beware of people who start throwing out model numbers or stating how many lumens you need. Avoid design-by-spaghetti -- people throwing something at the wall and seeing what sticks.
As a general rule, I try to stick with the 1w4h and 1w6h rules for selecting a
screen size -- there's also a 1w8h rule, but we try to avoid that. These rules are that 1 times width of the
image is as close as the nearest viewer should be, so for a 30' wide
screen, the first row is ideally 30' from the
screen. Then the 4h, 6h, and 8h are that:
+ 4 times the height of the
screen is the distance from the
screen for the farthest viewer in an "Inspection Viewing" application
+ 6 times the height of the
screen is the distance from the
screen for the farthest viewer in a "Detailed Viewing" application
+ 8 times the height of the
screen is the distance from the
screen for the farthest viewer in a "General Viewing" application
The farthest viewer ideally being the people sitting in the back row.
The reason I say we avoid the 1w8h rule, which would be for something like film-viewing is that in theaters, sometimes it'll be General Viewing, but other times a
presenter may want to put a presentation on the
screen that would be considered Detailed Viewing or Inspection Viewing. For those cases, we begin with the 1w4h and 1w6h rules, and if we need to free up space in the budget, we go the 1w8h. 1w8h means a smaller
screen, which is less expensive, and a smaller
screen means a smaller
image area, which means a
dimmer projector is necessary to illuminate the
screen sufficiently.
An example of how not to choose a
projector and
screen -- we recently had a client request a 30' wide
screen. They decided on 30' wide somewhat arbitrarily, but we didn't baulk at it because for their room it happened to perfectly place the front row at the 1w nearest viewer location, and the back row perflectly at the 6h farthest viewer position. They had been using a 20' wide and renting a 7000lm
projector. The 30' wide
screen more than doubles their
image size from the 20'
screen, so now to fill the
screen and maintain an equivalent brightness, they need a minimum 16,000lm
projector. I always thought the 7000lm they were renting was a tad dark, so I'd go as far as to say they should go to an 18,000lm or 20,000lm
projector instead of just the 16,000lm to be equivalent. Projectors of that class are more expensive, louder, heavier, require a 208v-240v
power source instead of 120v, and are harder to come by in the rental market.
I looked into regional rental rates at one of only two companies in the state we know of has projectors of that size -- their decision to go with a 30' wide
screen raised their rental fees for 3-day rental (which the local rental companies consider a week-long rental) for a weekend film viewing from $600 to $6000. I estimate they raised the installation price of the
projector and video
system infrastructure for their future video
system from $60k to $120k. Ten times the rental rate, twice the install rate. Bigger may be better, but you'll pay dearly to get it in ways that are not always apparent when you order a
screen.
If you want to contact me via PM, I'd be happy to put together some pricing for you on this. Don't know that'll be much cheaper than if you order something online, but I'd highly recommend ordering something like this from an audiovisual dealer instead of a website. There's a good enough chance you'll get a better deal, and you'll definitely get better service for things like warranty and repairs. You'll also get a better discussion and determination of which features and items are appropriate for your application.