It is my dream in life to own a tv-projector or similar.
I am taking for granted that the link below is full of rubbish,
but it got me thinking.
Are the prices of projectors reasonable or do they have an insane mark-up? It is actually possible to make one at home?
ordered one off of ebay a while back, I can tell you this:
it’s just a sheet of plastic made to work like a magnifying glass. I mean, if you hold it in front of your face, it will act like a magnifying glass. The whole process entails encasing the screen of your television in a box that’s completely black on the inside but with the far end left open, with the lens inside of that box, so that all light emitted by the sceen hits that lens. The light goes through the lens and is somehow(IANAPhysicist in any way) projected outward at a much larger ratio.
Simple idea I suppose. It does work, but it may not produce a perfect quality picture. I’d save up for the big-time projectors that you can hook into any video device, the ones that run about 5000 USD. Anyway, that product is not a scam, it does work.
It’s a big fresnel lens; results will probably be disappointing.
But there are lots of other fun things you can do with a big fresnel lens.
The site isn’t completely full of rubbish but you’re going to get the performance you pay for. Using a fresnel lens to project an image from an ordinary TV is possible but you’re going to see some glaring limiations. First a fresnel lens is bad for coherent images as it’s a conventional lens flattened by cutting it into concentric circular slices. You might optimize a fresnel lens for a point source but a wide source like a TV is going to make the rings obvious. Second you’ll see lots of chromatic aberration from using a single, single element lens. Red, green and blue cannot all be focused at once but it’s unlikely you’ll get an image good enough to tell much difference anyway. Brightness is going to be a big problem despite what the site says. If you projects a TV image to twice its size it will have one fourth the brightness.
That said, no harm in trying if you can find a fresnel lens and have some time to kill. I wouldn’t bother sending them £10 though. You’re just building a camera obscura with a TV screen where the film would be. Experiment in a dark room by holding the lens in front of the TV will tell you about where it needs to go. Just build a box to hold it there. Anyone that’s handy with tools should be able to build this in a few hours.
The main reasons people don’t consider this a real option for large-screen TV are:[ul][]Too dim.[]No rescaling of the image means you have big ugly scanlines.[/ul]I used to use a fresnel lens & a cardboard box to project animated fractals on my ceiling, though, and it worked well enough for that. Home theatre it ain’t, though.
Gotcha 
I once saw somone hang one of those lenses a little in front of their computer screen to get a 19" screen without too much quality loss, thought there might be something “extra” involved in that he suggested projecting with it.
What about the second part of the question? The practicalities of building a projector and the validity of their present retail cost?
Weep in jealousy, Iteki.
This is my new TV. People sit down to watch it and their jaws literally drop!
oh sweet holy god!
yojimboguy, that is literally larger than “screen 2” in my local cinema. I am agog! My shade of green is rapidly approaching the shade of the X-Box logo.
Congrats and well wear!
Thank you, I couldn’t hope for a better response.
I have had a nice 61" RCA for about a year now.
Makes me want to call in sick every day.
and playing X-Box on it makes the kids go wild.
Will X-box games still be playable on a shitty little 14" CRT set?
If not, any TV sellers reading this thread - pleeeeeeeeeeeease send me a nice big flat screen. Preferably LCD. The biggest ya got, thanks!
Not exactly on-topic but not all that off either.
A couple of weeks ago I borrowed a data projector from work. Hooked it up to my DVD player and an old steroe amp I had hanging around frmo my band days. Set up a makeshift screen in the backyard and turned everything on.
Well, the actual final result was better as I had to take this picture while there was still enough light.
The screen (if you can’t be fagged looking at the pictures) was 2.4m by 4.5m (which I think is around 8 feet by 14 feet) and when it was finally dark, make for one of the best outdoor movie experiences I been to.
We invited everyone around, had a BBQ, swam in the pool (this was a 38C (100F) day) and then watched the movie.
I would love to see some dark pictures of that Caught@Work, looks fab!
For various reasons I ended up living on the floor of a warehouse for a week (to protect our equipment for the exhibition we were holding there). My only demand in return for this was that I be allowed run the data-projector to my hearts content. Hooked up a load of speakers and played the movies all across one wall of the warehouse. Doesn’t compare to lying in the pool, but my lust for a projector began there.