Hello all,

I've been browsing these forums for a few days, trying to come up with a parts list for what I'll need to build my own projector. I've got a 17" LCD panel out of a BenQ FP71G+ that I was planning on using for this project.

I'm looking into what parts I'll be needing, and I'm really drawing a blank. I know I'll need a bulb, and the Ushio S400DD Lamp seems to be by far the most popular. As for ballast, the engaget article I'm using as a starting parts list (http://www.engadget.com/2006/10/17/how-to-build-your-own-hd-projector-part-1/) suggests this:
http://www.hidhut.com/catalog/400w-mhhps-1...l-may-p-49.html

Fresnels confuse me, I understand their pupose is to difract the light so that it can be focused by the lens (correct me if I'm wrong anywhere in this post, please) but the sizes confuse me. I'll be needing one that will be suitable for a 17" 4:3 LCD panel, whether it's 220mm, 620mm, or 330mm I have no idea.

Lens kits, what's the best one to go with? I'm shooting for a project budget of <$350, if I can. The ballast and the lamp will take up ~$150/180 of that, I estimate, so that leaves ~$200 for the fresnels, reflector, and the lens kit. I've heard great things about the LL Pro Projection Lens Triplet, but is that overkill for a first attempt? Are there comparable lenses for around the same price or less?

I ramble on, so for those who feel this is too long, and don't want to read it all, here's the summary so far:
- BenQ mystery LCD (I can look up the model number if I can find one on it, as I recall it wasn't obviously marked) $Free
- Lumenlab Pro Projection Lens Triplet $199
- HID Hut 400W MH/HPS 120/240V Digital Smart Ballast $119
- Fresnels (?) $???
- Mogul Base $15
- Ushio S400DD $39 from Atlanta Lightbulbs

As for how to use the Simple (haha) Focal caclulator, I'm lost. I'm looking for an average sized screen (whatever you think that may be) that can be projected from a distance of perhaps 10'-15' (??)

Any and all help is GREATLY appreciated!!!

Welcome to the forum!

Well... your monitor is a 17" 4:3 ratio monitor. Too large for the S15 sized (or similar) Lumenlab fresnels. That means you'll have to go with the Pro lenses (or similar). That's a 500mm FL triplet, 220mm collimator (condenser or rear fresnel) and 650mm FL collector (field or front fresnel). The length and width of your fresnels need to be large enough to cover your bare LCD panel (and maybe about half an inch larger). If you don't want to wait until Lumenlab gets their parts back in stock, you'll have to source them elsewhere. You'll be looking at somewhere around $250 for the lenses.

A comparable replacement for the 500mm LL triplet might be an 18" or 22" Beseler lens - if you can find one.

You'll probably be wanting to build a split setup (s you can keystone), unless your projector is going to remain perpendicular to the center of your screen.

As for screen size, most people shoot for about 120" diagonal (8' wide and 6' high). Building with the above mentioned parts, you'll have a throw from triplet to screen of about 12.8 feet. Your enclosure will be close to 3 feet long.

Any idea when Lumenlab will be getting more in stock? I was hoping to have this project completed within the next month and a half.


I agree that a Split Optics projector is where I want to head. I know that most of the 3' length is strictly for the focal length of the lens, but are there any tricks to trim that down?

I've read about removing the anti-glare layer from the LCD panel. Is this located on the front or the back of the LCD? Would you suggest removing it or leaving it on?

I'm hoping the other mods might be able to help you with this question cause I don't have the slightest idea.


Folding the focal length to the triplet lens using a front surface (fs) mirror, bare in mind fs mirrors usually have 96% reflectiveness at best. Stick with quality made which are usually thicker. Usually, you can salvage a good sizable fs from the lower portion of an overhead projector.


Always on front of the LCD, they are meant to reduce the glare from another light source like a ceiling/desk lamp or from an open window. And no, I suggest you do not remove this at all but rather polish it with Mothers Mag Polish or Peak Polish. I would actually STRONGLY suggest you use and enjoy the screen AS IS for now before considering any modification to the antiglare. It's rather risky mod that will allow things to go wrong even for a first build.

As an "other mod" I'd have to say that I haven't a clue, either. As moderators, our role here isn't really as part of the business end of LumenLab, out "job" begins and ends with keeping things in the forum within the rules.

Even answering questions here and elsewhere isn't "part of the job" -- that's something that we do because we have a genuine interest in this hobby. Most of the people who are moderators also happen to know a fair amount about it as well, since we've all gone through the process of building one.

For some of the other points...

Many people argue that unsplit optics will yield a superior image. This is technically true, because the fresnel lens (Which is really not that great a lens, optically) however having built both, I'd say that the real difference isn't noticeable. There are certain design considerationt to take into account however, and there are things that can only be done with one or the other design. For my pro lens build, and for the 10.6 build which I might actually get done some day, unsplit optics are the only way that I can see to acheive this.

For keystone correction, I advise people to not get too carried away with what they think is possible. I advise that you PLAN that the projector will have to be perpendicular to the center of the screen, with maybe a LITTLE adjustment from there, like 2-3 feet or so. People have done more, and gotten away with it, but it depends on how picky you are about your image.