My friend wants to buy a $2,000 video projector and project movies from his patio onto the side of his neighbor’s (white) house. (She’s OK with this.)
His patio is located about 30 feet from the side of her house. The idea is that we could show movies on this huge improvised screen, producing an image of about 20 feet across and by using the “keystone” image corrector to account for the upward angle.
Can a $2,000 video projector throw out the lumens needed to accomplish this feat, or are we tech-dumb dreamers?
P.S. How does the light output of a $2,000 video projector (DLP?) compare with that of a movie house projector?
My WAG is that this will not work very well. I have actually done this before, using bedsheets as a screen, but I did not put the projector so far away.
Beyond the brightness of the projector, you have to worry about ambient light. If this is a fairly well-lit neighborhood with street lights and such, you’re not going to get a very good picture. If there is a way to safely put the projector closer, you’d probably get better results.
No matter what the other answers to this thread say about the feasibility of your friend’s plan, don’t let them buy the $2000 projector before you know what the image is going to be like.
Rent a projector for a while, try it out. Wait till you’re sure, THEN they can sink $2000 into it.
I don’t mean to be a thread-stealer Carnac, but I’m interested in the same kind of setup (except it would be inside my apartment).
I’m looking at a sub $2000 projector, but probably not for about four to eight months (depending on how effectively I can save money). I imagine that current offerings will have changed somewhat by then, but, in general, what should I look for? How many lumens is enough? What else is important?
Any good websites out there with a nice beginners guide?
I suggest that instead of buying one, your friend builds his own projector. That way he can stand a fairly good chance of getting it to work, if not, he’s not out tons of cash. Here’ssomesites with the necessary info.
Yes, we want to check the feasbility before he writes the check. We’ve seen some video projectors, priced at upward of $7,000, that put out light like a light tower.
As for ambient light, his community is rather dark at night. No nearby street lights, though the stars do shine bright.
As a general rule, to get the required lumens, take the square root of your screen size (diagonal in inches), and multiply it by 70. Add some more lumens if you’re in a less than dark room.
Oh, a home projector doesn’t compare to a theatre version. Theatre bulbs are arc lamps and are measured in watts, not lumens. A typical multiplex bulb is 3k to 4k watts. You’ll have to do the math to figure lumens. I don’t know the multiplier, but I know it’s not a linear scale.
For those interested in video projectors for home use, just remember that replacement lamps cost $300 to 500. That’s 1000 to 2000 hours of viewing time per bulb.
I hope you are talking about your home movies. Because this is illegal if the “movies” are commercial films that you’ve bought a copy of.
Of course, a lot of people purchase or rent films, and invite friends over to see them. Without much worry about anyone reporting them. But you’re planning on showing them outdoors, projected 20’ wide across the side of a house. The chances of this being noticed and reported would be a bit higher!
I thought it was only illegal to show movies like this if you charged admission or made any money at all from the viewing. As long as they are not charging anything, how is this any different from showing the movies on a big screen tv in the back yard?
This is a good point, as I have a projector and was pretty shocked when it came time to replace the bulb. Projectors have internal timers in them, and many will plain shut down and tell you to buy a new bulb.
As far as the question goes, the answer is that yes it will work, but will it work well enough. To figure this out, I would rent several projectors with different light output. You will likely need a pretty powerful consumer model to do the job. Just rent 2 or 3 units of different output, compare, then make a buying decision. Remember that the further away the projector is from the target, the more power you will need. Same is true if the “screen” absorbs a lot of light (matte paint finishes would absorb/diffuse light more than semi-gloss).
Apples and oranges. Watts measure power consumption, lumens measure light output. Relationship depends on the efficiency of the technology. For example, a 20 watt fluorescent tube might be able to put out as many lumens as a 150-watt tungsten-filament incandescent bulb.
First of all, I think a throw distance of 30ft would be unrealistic for any consumer projector, the ones I’ve had focus out only to a 250" diagonal at roughly 350" from the screen.
Second, I doubt any $2kUSD projector will provide enough of the good stuff to reach out 30ft and give you acceptable photons.
And finally, unless the house in question is some sort of seamless concrete, the outline of bricks or siding panels will be quite horrendously annoying.
I’d say indoors is your only option for a commercial projector under $2k, but I’ve had fine outdoor results on moonless nights with a washing line, a white king size topsheet, and some beach chairs.
Your distance, surface, and size aren’t looking realistic though.
I have done exactly what you’re describing using a projector that my brother owns onto our neighbours white house. The projector cost £3000 so although I don’t know the model I’m assuming it’s similar to the one your friend is interested in buying in terms of specifications.
We were able to clearly make out the picture, at night, from a projected distance of about 40 ft and the image was approx 15-20 feet wide, bearing in mind there was some ambient street lighting about twenty feet away from the ‘screen’ the picture quality was reasonable. (I’ve seen worse picture quality on tvs using indoor aerials).
If the surface of the house is flat and painted white you shouldn’t have a problem.
I have to emphasise that although watchable, the picture isn’t great so realistically its fine for a bit of fun but not for serious viewing I’d say.
Have a look at “corporate” or conference-room projectors - they’re intended for use in rooms with the lights on, so they put out a rather bright image.
I borrowed one from work last year and had entirely satisfactory results at a roughly 30 foot throw onto a king-size bedsheet. This was an older unit that maxed out at SVGA, but it was entirely adequate for entertaining a campground.
Shouldn’t the lumens required scale as the square of the linear screen size, not the square root?
And how well this will work will depend greatly on the ambient light levels. If you’re out in the absolute middle of nowhere on a moonless night, then almost any projector at all would be adequate, but if you’ve got houses, then you’re not middle-of-nowhere. An eyeball gauge of “Yeah, it’s pretty dark around here” isn’t nearly precise enough to say. The simplest method would just be the empirical one suggested by beltbuckle and others: Try a few out, and see what (if anything) looks acceptable and what doesn’t.
I think theatre-quality image isn’t important. To my way of thinking, it’s the event itself that makes it so fun, not the actual image.
I stopped in Baltimore’s Little Italy a couple years ago and stumbled across an outdoor film festival. They used a movie projector to throw a truck-sized image about 70 feet.
Not killer quality, but quite decent.
BTW, I have no idea why high-end ($5,000) video projectors cost so much. The optics wouldn’t seem to compare with an amateur telescope. Any ideas?