Building your own projection tv

[Darth Sushi]

how much better does splitting the fresnal make the picture quality?

The collimating (or condenser) fresnel makes the light from the bulb run parallel through the LCD. You do not need this fresnel IF you are using a parabolic reflector. However, keep in mind that the light hitting the parabolic reflector will be parallel but the light from the bulb will be spirical. The collector (or field) fresnel is the opposite, which bends light towards a point. Both fresnels will affect the amount of light coming through as well as sharpness especially the collector fresnel. You can adjust image sharpness by trying different distances between the LCD and the collector fresnel.

[GepperRankins]

so should i split mine and put half in front of the LCD?

[Darth Sushi]

so should i split mine and put half in front of the LCD?

No, if you're using a regular projector setup. Moving the fresnel will change the focal length to the projection lens, which might make more problems. Yes if you're building your own box.

[GepperRankins]

well i've built my own box. i've got a feeling splitting the fresnal will get rid of darker edges and make the picture sharper, am i right?

[Darth Sushi]

well i've built my own box. i've got a feeling splitting the fresnal will get rid of darker edges and make the picture sharper, am i right?

Dark corners are usually due to problems with the reflector/bulb setup such as reflector size/type, bulb to reflector distance, etc.

[tracydani]

So how many of you finally joined LL or paid for an account?

[GepperRankins]

So how many of you finally joined LL or paid for an account?

not me

[Darth Sushi]

So how many of you finally joined LL or paid for an account?

Guilty

[GepperRankins]

well i've built my own box. i've got a feeling splitting the fresnal will get rid of darker edges and make the picture sharper, am i right?

Dark corners are usually due to problems with the reflector/bulb setup such as reflector size/type, bulb to reflector distance, etc.

i was just trying to split it now but couldn't so i tried putting it in front instead of behind and it looks a lot better

i thought the dark areas could be caused because with 1 full fresnal on only one side, the light is forced through the edges of the LCD at an angle. imagine yourself looking at an LCD from and angle, less light gets through

[Darth Sushi]

i thought the dark areas could be caused because with 1 full fresnal on only one side, the light is forced through the edges of the LCD at an angle. imagine yourself looking at an LCD from and angle, less light gets through

That's possible too. Fresnels usually just change the direction of light. But if the light hitting the fresnel already has dark corners, then dark corners will also be projected.