my first projector with the sgi 1600sw-NEED HELP

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got 8

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Joined 2005
#1
Hi all,
I started the project 2 weeks ago and almost done. sorry about not posting any picture but I do have pictures avery step of the project. I will post them together soon.

here is what I am using: in the order as I see them in the enclosure
reflector-ikea
400w hps retro-atlanticlightblub
lexan xl10-hd
330mm fresnel-3dlens
1600sw lcd
550mm fresnel-3dlens
25"fl(635mm) loooong throw lens-about 8"dia x 4"long

the problem I am having is edge focus; I can see subpixels in middle but the edge is very blurry.
at first I thought its my obj lens problem so I tryed with a 15"fl lens still the same.
So I am thinking could it be my 550mm fresnel is not a good match for my 25"obj lens.
Please help with any other sugestion, I ll get a screen shot tonight.
thanks
got 8
 
#2
Im not too keen on all the projector mathematics but start by makeing sure everything is centered. You can also try moving the frensels closer to the lcd and making the distance between the light and the frensel alittle less than its focal length and make the distance between the projection lens and the foward frensel alittle less than that focal length. Other than that having everything centered is KEY.
 
#3
I dont think picture will show the details with the 100k attachment.
if someone can host it for me? I will see it through email.
at the meantime I will align the lens better and adjust the fres to lcd.
anyway here is a couple to start:
notice the texts in the second pic start to blur toward the edge.
 

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#5
You don't say how far you are projecting or how big a screen you are getting. If you wanted a 100 inch diagonal screen, then the projector would be 14 feet from the screen and the fresnel would have a focal length of 750mm. So at those distances the 550mm fresnel is not the best for your setup. As for your blurry corners, is the fresnel perfectly flat and not warped at all?
 
#6
Mikey p said:
You don't say how far you are projecting or how big a screen you are getting. If you wanted a 100 inch diagonal screen, then the projector would be 14 feet from the screen and the fresnel would have a focal length of 750mm. So at those distances the 550mm fresnel is not the best for your setup. As for your blurry corners, is the fresnel perfectly flat and not warped at all?
Click to expand...

the throw distance is 16.5' feet
I have calculated the lcd to front fresnel to be 2.75" apart.
these are new fresnels they are very straight, dont know the quality.
so you think I should try alonger fl fresnel?
 
#7
The focal length calculator I'm using shows that with a 2.75 inch gap between the lcd and fresnel, a 16.5 foot throw and a 635mm lens, then a 650mm fresnel would be ideal. Your projected image will be around 130 inches diagonal. But your issue is blurry corners. It's the triplet that has to focus on the lcd. The fresnels job is to direct the light. I'm wondering if the problem is your triplet doesn't have a wide enough field of view for this application. The focal length calculator states the triplet field angle needs to be 37.5 degrees. Where did you get this lens from? Are there any markings on it?
 
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