The best sized lenses

Hi guys,
I have a question for ya. If I got ahold of a 98mm big screen TV projection lens, would that be big enough to project a 14" LCD screen?
Its a PCX, so would this mess up the projection onto a flat projection screen? For that type of screen, I don`t know if a flat lens or a PCX is better.

Thanks for your help,
Mitch
 

xblocker

Member
2001-12-20 5:10 am
Mitch,
1. it depends of the focal lenght, which in your case should have minimum panels diagonal size (14")
2. as stated over and over , a single lens always have spherical abberations, which don't let you focus the complete image properly. So a single lens can only give a rough projection quality.

BTW, what do you mean with PCX vs plan lens?

xblocker
 

jason1971

Member
2002-06-07 9:47 pm
I think I'm going to need some clarification here. Do we need in all circumstances a lense with the focal length of the screen's diagonal, or is that only in the case of not using a fresnel lense to project the light path down. Please correct me if I'm wrong, but I have been working off the assumption that we use the fresnel to condense the light path down to a smaller size so that the lense we use to project the image is fooled into thinking that the image is actually smaller. I know this is basic stuff and I should know the answer for this, but I guess I just have to ask because I just may have completely gotten this wrong.
 

xblocker

Member
2001-12-20 5:10 am
jason1971,
the lens formula would allow you to make focal lenght smaller, but this is only a mathematical question. Lenses, the thicker they are, add more and more optical distortion to the image, so that they need specialized correction elements! Like fish eye objectives.
If you look at optical instruments, bigger objects need longer focal lenghts (opaque projectors, OHPs). Also big format photography uses longer FL due to this optical problems. Fresnel lens only does illuminate the image path and has no imaging tasks for projection.

xblocker
 
What i mean is since the PCX has the curved lens, I didn`t know if it would screw up the image on a flat surface screen.
Wait a sec. Are you saying that for a 14" monitor, I need a lens with a 14" fl? And these correspond like this all the time for optimal performance? This is something I didn`t know...
I guess theres a lot I don`t know.