Hi at all
I am building a vertical 15" standard lumenlab lens and fresnel.
I am a little confused regarding the distance from the lcd and the triplet.

The focal length is 320 so I assume that the distance from the lcd would be 320 mm from the center of lcd till the back of the glass of the triplet.
But in the plans http://www.lumenlab.com/forums/index.php?showtopic=15460 her show a slightly bigger distance 167+177=344 mm

which is the correct one?

I supposed to place the triplet at 320 mm + or - 20 mm for focusing but were is the place were start to measyre the distance in the triplet , the back , the front or the miffle of lens glass?

Thank you
Andrea

The guide is just that, a guide. Plug your dimensions into here and you'll get a more accurate result. Remeber to leave adjustability in everything in the optics. You will need it.

Thank you for your answer,
I already read yor great guide but some point is not clear to me.

I made some calculation.
it seems that I have to put the lcd 355 mm away from the triplet and I'll obtain a screen of 3500mm of diagonal
but I'd have to put the projector at 3000mm form the screen ..is it correct?

THe problem is that my best setting would be the projector 4500 mm form the wall is it possible?
My wall is a maximum diagonal of 6000mm

Thank you for your help

Yes, it appears you calculations were correct. One problem of the 15" LCD's using the standard 320mm FL triplet is that the throw is short, meaning the PJ gets located in front of the seating position. Try the running the numbers using the Pro Lens set (500mm FL triplet and 650mm FL front fresnel). This will move the PJ further back for the same screen size.

Hope this helps.

cheers,
gs