Hi again,
I'm using a 17" lcd to gain hdtv resolution. I have a ohp with 575w metal halide lamp. The ohp has a dual focus fresnel with 310mm/470mm focual lenghts. The triplet projection lens is 300-340mm variable focus.
In the light assembly there is a very thick lens in front of the lamp. There is also a second condenser lens that via a swith goes in front of the first lens. I belive there is an increase in brightness when using the second lens. I am not sure on the focal lengths of these lenses.
This combination worked fine but because of the size of the fresnel it didn't use the full lcd.
I've now just received the 15.5" fresnels from diyprojectorcompany (diylabs). These are larger then the lcd so it covers the whole screen without any loss in the sides. 🙂
The new fresnels come with focal lengths of 218mm/326mm.
When combining the new lenses and putting the light source and the projection lens at the correct focal points I receive a sharp projected picture but I acually see less of the lcd then before! 😕
I'm not sure what exactly is wrong.
1. The condenser lens on the light source does not work with the focal length of the fresnel.
2. The focal length of the projection lens does not work with the focal point of the fresnel.
But the triplet lens should work since it has 300-340mm focal point. But then how did it work before with the original fresnel of 470mm focal point. 😕
I've looked at various threads for the answere but I still don't understand whats going on.
Would anybody know how I can fix my setup so that I use the full size of my lcd.
I'm very close to breaking down and using the original ohp setup and only part of my lcd screen size. HELP....
Exipnos
I'm using a 17" lcd to gain hdtv resolution. I have a ohp with 575w metal halide lamp. The ohp has a dual focus fresnel with 310mm/470mm focual lenghts. The triplet projection lens is 300-340mm variable focus.
In the light assembly there is a very thick lens in front of the lamp. There is also a second condenser lens that via a swith goes in front of the first lens. I belive there is an increase in brightness when using the second lens. I am not sure on the focal lengths of these lenses.
This combination worked fine but because of the size of the fresnel it didn't use the full lcd.
I've now just received the 15.5" fresnels from diyprojectorcompany (diylabs). These are larger then the lcd so it covers the whole screen without any loss in the sides. 🙂
The new fresnels come with focal lengths of 218mm/326mm.
When combining the new lenses and putting the light source and the projection lens at the correct focal points I receive a sharp projected picture but I acually see less of the lcd then before! 😕
I'm not sure what exactly is wrong.
1. The condenser lens on the light source does not work with the focal length of the fresnel.
2. The focal length of the projection lens does not work with the focal point of the fresnel.
But the triplet lens should work since it has 300-340mm focal point. But then how did it work before with the original fresnel of 470mm focal point. 😕
I've looked at various threads for the answere but I still don't understand whats going on.
Would anybody know how I can fix my setup so that I use the full size of my lcd.
I'm very close to breaking down and using the original ohp setup and only part of my lcd screen size. HELP....
Exipnos