I subscribed to the forums because of a particular problem the media room in my new house presents. I would like to have the projector much much farther from the screen than the focal length of the standard or pro lens triplets will allow.

I thus need a "telephoto" or "zoom" type lens arrangement. I've searched and read the various threads regarding this but they seem more theoretical than experimental.

I'm interested in hearing if any of you have actually created a telephoto or zoom lens arrangement and would like to pick your brains on some particular questions if you have.

Thanks
Brooks

And, BTW I don't care about the resulting size of the box - I've got plenty of room for it

I'm afraid you would have to design it yourself, and do a ray trace on it or maybe reverse engineer a commercial lens and scale it up to what you want.

Joe

Lucky-me has some 32" fl triplets He might not use. They may be a litlte spendy and you will need a long fresnel from a big screen tv but with a 15 LCD you could throw 30' or so.
It can be done.

I have some very long throw lenses, but I don't plan on parting with them until my projector is complete or nearly complete.

If you want to build a telephoto lens, go buy a concave and a convex lens. Plave them in front of your triplet and viola, you will have a telephoto system. If you are going to ask me what FL's to buy, I have'nt a clue. Probably longer would be better I would think. I have experimented with this but I keep chipping lenses so I have to wait until I have better system in place and the PJ is 90% done before I can test further.

You could take apart a cheap ($70-$100) telescope. They usually have reasonably good optics and long focal lengths. I've got one that's 60mm X 700mm that I'll be using for a test build.

i may accidently have some super-long throw triplets coming int the mail... I made the mistake of bidding on a set ofthree projector lenses on eBay. They're about 4.5 inches diameter and about 17 inches long... these suckers have a really long throw, and they weigh a ton at around 14 lbs EACH .

My main problem is with shipping (probably around upper $40 lower 50's), and not the actual price (right now it's going for $20). I'm actually hoping I don't win them, because shipping is so much.

At any rate, if I do win them, I'll be selling them in the Trade section of the forum.

ebay item # 7579782755

you can find a pdf of the specs if you search for the part number in google.