Hello LL! My name is O'Malley. I have been a long time lurker and have just signed up to finish off the research for my build. I have most things figured out but was looking for some input.

I haven't decided wether or not I want to go split or unsplit. I understand that with split I can position the fresnel so that keystoning is not apparent (?). I plan on having my projector relatively level with my screen and was curious what the benefits of a split screen are (besides the mention of keystoning above)?

I also was looking at a device that changes the signal from a console or DVD player (RCA?) to VGA. I have seen some devices but wanted some community member input. Any information or direction is greatly appreciated.

Thats it for now. Thanks for the help.

O'Malley

I believe that keystone correction is in fact the only benefit of the split set up. split fresnels generally have a lower quality image than unsplit due to the fact that when the image passes through the second fresnel it causes slight distortions in the image. since your projector is going to be near the center of your screen, I would personally suggest using un-split fresnels. You could also look into lens shifting in the pro guide.

I haven't completed my first build yet, but i've been playing around with a philips e-box ftr9964 with my 15.4" LCD and I think that the image quality that it produces is fantastic and i believe others have had good results with the 9964 and the 9965

I can think of one other issue requiring a split fresnel setup. It concerns a problem I ran into. With an unsplit setup, if there is too much of a difference in the focal lengths of the triplet and the condensing fresnel, the light throught the fresnel may not converge at the optimum point within the triplet, giving less than the brightest possible image. I'm using a 327mm OHP triplet with a 317mm Lumenlab fresnel, projecting a 72 inch diagonal image. Using unslpit fresnels, my PJ's image was focused, but on the dim side and a little yellow looking. I moved the condensing fresnel to the other side of the LCD, which put it about 38mm closer to the triplet. That gave considerable improvement to the image. I have since "played with" the spacing of the fresnels and seen how the focal lengths of both the triplet and fresnels must be taken into consideration. Also, the size image you are projecting comes into play, too. Remember, the larger the image, the closer the triplet will be to the LCD to maintain focus. I may not have had my brightness issue if I could have used a larger projected image (thus, allowing the triplet to be closer to the LCD), if I'd used a triplet with a shorter focal length, or if my condensing fresnel was 330mm rather than 317mm.

All that being said, don't set your plans in stone. Allow for experimentation and modification.

Hope this long reply is helpful.

Thanks for the halp! I had understood that once you have the fresnel in place the size of the screen is determined by how far away the projector is away from the wall correct? I plan on building a focusing mechanism but I'm trying to figure out other things at the moment.

@simp1yamazn: *EDITED* Found the answer to my question.
O'Malley

Yes, the size of the projection is determined by how far the projector is from the screen. However, to keep the image in focus, the triplet lens must be moved closer to the LCD if projecting a large image, and further away from the LCD if projecting a small image.

If you move the PJ closer and closer to the screen there is a point where the triplet will be the same distance from the screen and the LCD and both images will be the same size too.

Make the distance longer untill the image is on the screen is twice the size of the LCD and the triplet will be 50% closer to the LCD.

The triplet will always be further away fron the LCD than the focal point. For small screen setups the triplet will be further from the LCD than you might think to get focus, A 327mm reiplet can be at 400mm and a 500mm triplet can be at 600mm or so.

A split system might make less glowies in most setups. You will get a little more throw from a un-split system.

I went with un-split and I like it. I do have some glowies but I don't see them much.

Thanks again. I plan on making a focusing system for my projector (2'' movement overall).

Also, glowies? If you wouldn't mind explaining or directing me to where this is explained that would be great.

O'Malley

the thread on improving glowies is here

Thank you for the link. It helped me alot on my quest of building a pj.

O'Malley

I'm back with another question. Does anyone know of a link that explains the focal calc? I have a few questions that I would like answered. If there isn't I will post my specific questions later.

O'Malley

*EDIT* I am currently looking at purchasing the Sony SDM-HS53 15'' monitor. According to the compatible monitor database it says that it has FFC issues. Are monitors with these issues easily fixed or not? Thanks for the help.

**EDIT** I figured out the focal calc. Above focal calc. question no longer needs answering.

Well, unless you have some decent experience tearing computers and monitors specifically apart and rebuilding them successfully, I would decline getting one with an ffc issue. I know I ruined a new $110 monitor from new egg trying to fix the ffc issue. They are very flimsy and I wouldn't recommend playing with them more than a couple of times before they are installed in a final set up. SERIOUSLY, these things are barely soldered on, and impossible to resolder without extensive experience.

Go with one of the recommended ben-q's, it'll save you money in the end by getting it right the first time.

I have been having problems tracking down 2 of the same monitor. I need two of the same becuase in the process of building mine I have to teach someone else how to build one (to get school credit for the build). Long story behind that. I do have experience with electronics and soldering (I mod 360s for people). I will look for a monitor without ffc issues then. Thanks for the help.

O'Malley