I've been pouring over the forum and have found many helpful resources and plans.

From what I've been able to find, it seems people have a 2" (50mm) travel in their lens for focusing.
Is this correct for the LL standard lens?

If so:

The LL lens-fresnel kit has a forward fresnel with a FP of 317mm. Which would put the triplet lens about 307mm away correct? (According to most specs the front fresnel is 330mm and the lens would be 320mm away)

Should I have the lens set for 1" (25mm) forward travel and 1" (25mm) backward travel? I wouldn't think this would work because if the lens itself was at the dead center of the 50mm travel, it would be 307mm from the front fresnel lens. If you then extended out to the fullest distance from the front fresnel, it would be 332mm away which is beyond the front fresnels focal point.

I hope this is clear. If not I can probably whip up a diagram to explain it better.

Thank you in advance for your help.

It's been described to me like this.

Your projector consists of two major components:

1. The light engine
2. The projection engine

The light engine is the lamp and frezzies.

The projection engine is the LCD and triplet.

So, you use the calculator to determine - based on your particular desires - where best to position your LCD in relation to your triplet. (Split versus unsplit I will not go into.)

This is where your focus comes into play. There are various and sundry methods to focus. SupraGuy made his LCD moveable so he could optimize his light engine with respect to his triplet for premium light output and focus by moving his LCD (instead of his triplet).

This brings up the point about the interaction of the light engine with the projection engine. Depending on how your lamp is "projected" into the rear of your triplet your projection illumination will be greatly affected. An image of your lamp's arc chamber is "projected" through your triplet and the details of the geometry of the entire setup determines the intensity and homogeneity of illumination on your wall screen.

So, in the end, a kinda generic way of building is to allow for an inch of adjustability either way (fore and aft) to allow for final tweaking of your projector.

It's actually best to allow for "as much adjustability as possible" but that's a bit of an extreme statement taken completely literally but it gives you an idea of what you really need to do to get the absolute best build.

Hope that helps a little.

Also, keep in mind that even though you are buying a "220 mm" focal length fresnel (or whatever) it's not necessarily EXACTLY a 220 mm focal length. Again - adjustability is key.

Use the calculator to decide how far away to make your triplet from your LCD - NOMINALLY.

Separate your fresnels at least the minimum recommended distance.

Allow for some fore and aft adjustability of your lamp and also some lateral movement so you can get everything perfectly centered along the axis of projection.

Keep your LCD at least the minimum recommended distance from your front fresnel to avoid projection artifacts (assuming an unsplit build).

Keep in mind fresnel focal lengths are not precisely as stated by vendor. There is some slop. You can determine that more closely through home experimentation.

I think that's all sound advice.

I did download the focal calc a little while back and did some rough measurements last night. I was amazed to see how large the projection would be based on where I was planning to place the PJ. I'm rethinking that already.

I will be going with the split lens setup. So while I like the idea of SupaGuy's setup, it won't work for me. But I give him serious props for coming up with a rather unconventional design.

This will be my first build, so I'll be keeping this one rather "Generic". I'd like to do a vertical setup, but I'm concerned that the addition of a mirrior might make my first build just that much more complicated.



I am planing to make as much of the interior as adjustable as possible. I'm working on a design that would fix the lcd to the sled, and make both fresnels adjustable. The front frensels 4 corners will be able to be manually adjusted to allow for keystoning correction. I've attached a diagram of my plan for the sled. A bolt will travel through the rear fresnel and be locked in place with nuts. The bolt will then run through the lcd frame and again, be held by nuts. This allows me to adjust the distance between the rear fres and the lcd. Then the bolt wil pass through the front fres' frame with a spring seperating the two, and a wing-nut holding the fres in place.This give me the ability to adjust each corner as much as I want. To ensure the front frame will tilt I'm going to need to drill the holes larger than the bolt to allow for the angle of tilt. I'm working on an idea of sliding a rubber o-ring in that hole with an inner diameter matching the bolt, and an outter diameter matching the hole.

Click to view attachment

I haven't figured out how to get the light/reflector to be adjustable yet on 3 axis. I'm looking over some other designs. But so many people have so many different ideas.



It does, thank you.

Mostly it sounds like it's a "figure out a you go along" process. The theory is there, and the basic specs are set. But the total process is just tweaking everything just to get it perfect.

Sounds like you'll be just fine. Keep in mind the mirror also has been shown to reduce brightness as well as being another bit to tweak "just so" to get optimal results. But, having said that, I must also point out there are superior builds here that are the envy of many and they use mirrors so don't write it off out-of-hand.

Best of luck! Need more help just ask and someone will eventually chime in.