Buhl 22" FL(559 mm) Opaque Projector Lens
I have just aquired a 559mm Lens from an old Buhl overhead projector. Anyone know what Fresnel combination I would need to be able to project from 17 inch panel? I'm looking to fill a 110 inch diagonal screen.
Any suggestions would be appreciated. Apparently the DIYPC 330/220 combo doesn't work.
I have just aquired a 559mm Lens from an old Buhl overhead projector. Anyone know what Fresnel combination I would need to be able to project from 17 inch panel? I'm looking to fill a 110 inch diagonal screen.
Any suggestions would be appreciated. Apparently the DIYPC 330/220 combo doesn't work.
You've got a great lens there, it just happens to match the new long focal length fresnel from 3dlens perfectly.
Check out 3dlens.com with the 220mm (#A310b) 550mm (#F550) combo...
link
If you use the two fresnels in a split design then you can get a 110" screen if you place the projector approx 164" from the screen (that's the theory
)
Check out 3dlens.com with the 220mm (#A310b) 550mm (#F550) combo...
link
If you use the two fresnels in a split design then you can get a 110" screen if you place the projector approx 164" from the screen (that's the theory
)Actually, you're gonna have to play around with the distances or get a longer FL fresnel.
Throw = (Screen Size) x (FL) / (LCD Diag) + FL
Throw = (110) x (22) / (17) + (22)
Throw = About 164"
BUT! The LCD to projection lens distance is:
1 / (LCD to Projection Lens) = 1 / (Projection Lens FL) - 1 / (Throw)
(LCD to Projection Lens) = 1 / (1 / 22 - 1 / 164)
LCD to Projection Lens Distance = 25.4" or 645mm.
A 550mm Fresnel is too short with these numbers. You'd need something like a 630mm (split design; place field fresnel 15mm before the LCD) or a 660mm (unsplit design; place field fresnel 15mm after the LCD) to match up the distances.
Throw = (Screen Size) x (FL) / (LCD Diag) + FL
Throw = (110) x (22) / (17) + (22)
Throw = About 164"
BUT! The LCD to projection lens distance is:
1 / (LCD to Projection Lens) = 1 / (Projection Lens FL) - 1 / (Throw)
(LCD to Projection Lens) = 1 / (1 / 22 - 1 / 164)
LCD to Projection Lens Distance = 25.4" or 645mm.
A 550mm Fresnel is too short with these numbers. You'd need something like a 630mm (split design; place field fresnel 15mm before the LCD) or a 660mm (unsplit design; place field fresnel 15mm after the LCD) to match up the distances.
Wow I really didn't realise that, I had always assumed that the fresnel had to match fairly closely with the triplet, like the specs over at lumenlab
Lumenlab
They use a collimator fresnel 220 mm fl, and matched 317 mm fl fresnel with a 320 mm fl triplet.
well if you're looking for a 630 mm fresnel here you go
HR1002
Lumenlab
They use a collimator fresnel 220 mm fl, and matched 317 mm fl fresnel with a 320 mm fl triplet.
well if you're looking for a 630 mm fresnel here you go
HR1002
I thought the same thing until it was explained to me (thanks Guy). For some reason, the LCD to projector lens distance will always be longer than the projection lens' focal length. That's why matching up the fresnel to the projection lens is hard. Limited number of fresnel focal lengths available.
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