I've built an inverted vertical folded (light at the top, mirror/lens at the bottom) to test a passive cooling idea. I'll post a plog as soon as I'm happy with the results.

1. Lamp type - Venture 875W MH MS (no reflector, probably why things are dim)
2. Distance to rear fresnel - 330mm
3. Rear fresnel focal length - 330mm (3DLens)
4. Distance between front and rear fresnel - 12mm
5. Front fresnel focal length - 550mm (3DLens)
6. Distance from front fresnel to LCD - 20mm
7. LCD diagonal - 17"
8. LCD model - Samsung 740N
9. Distance from LCD to projection lens - varies around 550mm to achieve focus
10. Focal length and diameter of projection lens - LL Pro 500mm/100mm
11. Throw distance to screen - varies to fit the image in a 48" high screen (10' max width)

I am still adjusting the mirror to eliminate left/right keystoning -- that might fix the problem which is: all objects with 'hard' edges in a projected 1280x720 image have a halo or ghost to the right on the screen. I don't see any artifact on the LCD screen the the unit. For example, when the XP desktop is displayed, the folders and icons on the left of the screen have faint halos (maybe two or three repitions of their right edges).

The fresnels are oriented right (that removed the dark ring) and the pro lens has its rim toward the mirror (that helped the brightness and the focus big time) and the fs mirror is the right way out (reversing the mirror makes everything fuzzy).

So what did I miss?

Thanks

Are you connecting the projector to your computer with a long VGA cable? I have seen "echos" on the right side of edges like you describe when using an inexpensive long VGA cable or an inexpensive KVM switch. If that's the cause, you can tell by turning down the resolution. In such cases, the ghosts go away at lower resolutions.

Right on -- an inexpensive 25' sxga cable. I relocated the PC so I could use the 2m cable that came with the 740N, and voila -- no halo (and better colors to boot).

Thaks,

aye analog VGA signals don't like to travel long distances. digital DVI can travel much further without issue. glad you solved the problem

I am having the same problem- I made one of the VGa cables with 50' of Sheilded Cat5.

The problem is, I don't really have any way to get the computer any closer. I could get away with a 25' cable.

What do you suggest?

A. Cut down the cat5 to the 25' ?

B. Buy an actual VGA cable?? If so, are the monoprice ones good? Would the VGA cable be better than the cat5?

C. Something else???

I've always been leary of the cat5 to vga cable idea.....where I work we have purchased a bunch of the 25' kvm cables from monoprice and are quite happy with them, we had some EXPENSIVE cables that we got from startech and to me anyway the monoprice ones might even be better....but those are kvm cables and not just vga cables.

Try and add some ferrite cores to the ends of your cable help shield against interferance.

Could I get around this problem by running a 25' DVI cable from my PC, then attaching a DVI/VGA adapter, then a 5' VGA cable into my Projector?

Like this:

[PC]====25' DVI Cable ====[DVI/VGA Adapter]===5' VGA Cable===[Projector]

it would probably help

I assume you mean DVI-I which contains both digital and analog, in this case its do different than VGA cable, better cable may help but a DVI-I cable with a VGA adapter isn't doing anything new. Using the gigital side of DVI and converting to analog (VGA) at the monitor would help but those boxes are $200.

didnt think of that..