running some numbers through focal calc i have come up with the fact that the triplet needs to be 563mm from the lcd. i am unsure though which part of the triplet this means though, is it the begining of the back of the triplet or the centre?
please advise!

thanks

If you have the regular LL triplet I'm pretty sure you go by the center. I'm sure someone will correct me if I'm wrong..

Thanks, do you happen to know if the same applies for the pro triplet...i would imagine the principles would be the same but you never know!

Your best bet is to make it as adjustable as possible, then you can be assured of the best results. Also, as you move the projector (for instance if you want a bigger/smaller screen image), you'll need to be able to move the triplet in and out to get perfect focus.

thats exactly what i hope to achieve...eventually at least.
was just trying to get a rough idea of where it is needing placed so then can incorporate some movement either side for fine tuning.
thanks for your help.

The best advice I can give is to get a measurement from the front of the triplet to the back of the triplet and use this measurement as the distance of travel in your triplet adjustment. I know it is over kill but IMO if i decide to change lenses it will give me more flexiblity on options. Standard S15 most recommend the center of triplet, beselers farther to the back, I would asume that most long throws will be to the back more than the center. Maybe one of the lens experts can confirm or correct me on this.

To get a closer measurement of the ture distance I would place a mark or tape a X on the place were the lcd is going to set and get your triplet to focus on to it as sharp as it can get then take a measurement to that spot for the triplet center point.

The focal calc gives distances to the optical center of the triplet. If I were a more patient person, I could tell you where that actually IS, but that would require that I build a test rig. It would also require that the actual FL of the triplet be accurate to the micrometer, which is often not the case. (GASP! Can this be True? Of course it can. It's called manufacturing tolerances.)

So, leave a little bit of adjustment room for the triplet.

My initial impression of the optical center of the pro triplet is that it's about 1/3 of the way up the barrel, closer to the flange. If you leave about 30mm each way for adjustment from there, you'll be set.