rear projection tv lenses

[toguko]

I am looking for lens that would cover 1700mm at infinity. Obviously these kind of photographic lenses don't come cheap (if you can find one). A friend of mine suggested I try rear projection tv lenses. I thought if they can cover 60 inch tv screen, maybe they would be good. But I can't find any information about focal lengths, view angles nor image circles for them. I was wondering if anyone played with one of these and could tell me more about them.

I saw this thread and it's kind of promising:
http://www.largeformatphotography.in...x5-camera-ever!!!

and here are some examples I have in my mind:
http://www.ebay.com/itm/Set-of-3-Del...-/111312040406
http://www.ebay.co.uk/itm/Barco-Data...p2047675.l2557
http://www.ebay.co.uk/itm/BARCO-CLM-...item2c6ec02e0a
http://www.ebay.co.uk/itm/Barco-R984...item35d44eea02

I would appreciate any constructive information.

[Carsten Wolff]

They may be better than the old 3-lens video projector lenses. I think I have one of the latter, a TV-Fujinon. Super-fast (145mm f1.2) but rear flange to film distance perhaps 15mm at infinity. Mine just covers 4x5" at portrait distance on ye olde Speed-Graphic, but doesn't do infinity without tricks anyway. Here is (was) v.1 of it (before I started to swap things over....).



I suspect you're approaching this from the wrong end so-to-speak anyway:...The projected image of the lenses you're talking about may well be 60", but the image source is smaller than your standard 4x5". Go pinhole if you need coverage.....

[erie patsellis]

The Delta series of lenses has an aspheric front corrector, used for adjusting edge focus originally. By removing the front corrector (two studs screwed into plastic) the back focus increases significantly, on my HD144 lenses to about 5 or 6 inches at infinity. Front projection lenses will work better in my experience, as most of the rear projection are liquid coupled with part of the optics incorporated into the front mount of the tube. For a good idea of what lenses are available, see http://www.curtpalme.com/forum/viewtopic.php?t=2761 (though I'm sure that few, if any will have any idea beyond the original use)

[Amedeus]

I've taken a look at plenty of rear projector TV lenses out there and never found anything that would cover few feet at infinity. As Carsten already stated, rear projector lenses do start out with a small (~3/4") light plane and magnify this over a short distance to the size needed. Kind of like a macro "magnifying" application in reverse.

Some lenses will cover 4x5 though.

[toguko]

thank you very much for making this clear for me.