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Same diagrams as above in PDF format.

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I'm using the pro lens triplet, does it really matter which way it faces?

The arrow in the diagram shows the direction of the light travelling from the lamp to the screen, therefore the flange should be facing inward (ie. mounting flange will be closest to the LCD)

cheers,
gs

It's good to see that there's concensus on this issue!

I'll try flange pointed in and see how it looks.

Is there less of a curve on the lens closest to the flange or is it because it's recessed in the housing in the picture?

Yup, flange definetly goes closest to LCD. That cleared my out of focus corners right up.

Flange towards LCD

Hi,

First off, I'm a newbie here.

Secondly, I'm wondering how to search for a used lense on ebay to save some money in the build process. I've searched ebay for projection lenses and a bunch of results come up. I can't tell which ones would work for the basic 15" projector design.

Do I only need one that states 100mm? Or does it have to be a triplet? Are they all triplets?

Any help would be appreciated.

Thanks,
E.P.

most 'projection' lenses on ebay are probably triplets.. you definitely want a triplet.. not a singlet, meniscus, etc, since they suffer greatly in terms of image quality. a popular triplet on ebay is the Charles Beseler 18" EF.

unless 100mm is the lens diameter, its way too small. focal length of 100mm will give you a gargantuan image from small distances (think 500" from 10 ft or so ).

Thanks for the quick reply. I'm going to buy it off of Lumen Labs for my first projector that way I don't run the risk of fowling things up. I appreciate the help.
-E.P.

I haven't taken one apart or anything, but is there anything stopping us from disasembling the pro triplet, flipping the lenses around, and reasembling the triplet? That way we could have the flange on whichever side we want.

elken did just that so the lens would better suit his build.

Consider this an EXTREME MOD!! Be careful. Be clean. (You'll be voiding any warranty.)

I'd have to say it's NOT RECOMMENDED but it's doable.

Hey, I just wanted to say the link doesn't work.

Do 3D model exist for these? If so they should be converted and uploaded to Google's 3D Warehouse via Google Sketchup. I'm trying to get the library going.

I put up models for the standard and the Beseler 18" triplet. Search sketchup 3d warehouse for "Lumenlab".

That's because there is no link.

Hi,

is there a reason why the two FRESNEL lens need different focal lengths?

This is *SO* not the place for that question.
Read the guide. http://www.lumenlab.com/forums/index.php?showtopic=8972