today I took of the original polar off the lcd and put a SHC polar in front of the triplet. it was the worst image I saw this my pj put out.

my setup is a 17" vertical folded. I dont have enough polar to cover the whole screen. when I place the polar on the screen then the reuslt is good, but when I put it anywhere after the mirror the image gets messed up ..

in the title I said it gets colorized but it is more like a mixed negative/colorize effect which is only visible in black and only on the top half of the screen .... !

I have no idea what the problem is, but if I can fix it I'll turn the lcd upside down and with the side without the polar facing the lamp and put my small piece of polar after the lamp before the lcd ... and flip the image with the computer.

anyone have any ideas ...

where did you get the film, it apears to me you do not have the angle right to match the other polarizer. rotating it will give negative picture in one direction and good in another.

polarizers on lcd's are either 90deg. or 45deg.

can you show a picture of projection, and also picture of your lcd setup. and telling which orientation you have of the lcd ie which way was the original anti-glare facing, if it is a vertical design, then i take it that it is facing up, and this is why you can use a polarizer neer the projection lens.

the films are from polarization.com .. well if I put the film on the triplet then what ever angle I try I cant get the right image... see image 2 (this is the best it gets at the triplet)

this is the film on the lcd .. no keystone here .. the "marks" on the screen is the glue residue from the polar removal ... I couldnt wait to try out the new film .. so I'll clean it up later ..
Click to view attachment



this is with the polar on the triplet .. like I said the best it gets. playing with brightness/contrast helps abit but no where near to what its supposed to look like ... inside the red line towards the top of the screen indicated where the problem is most visible .. you can see the top of the screen - the letter box is red in real ....

by the way the darker area with in the read line is the glue residue again ... has nothing to do with my problem ...
Click to view attachment

yes the lcd is facing up - I removed the film on the side facing the triplet ...

I think you should try to remove the rest of the glue residue. It looks to me as though it is acting as a retarder, slightly rotating the polarization so some of your screen is polarized at a different angle than the rest.

DJ

the thing is the areas where there is no glue residue (below the red line) is also no good ... also the in the first picture where the polar is sitting on the fresnel, half of it is on the glue residue ... you are right when I change the angle the area with the glue looks different than the area with out ... but overall at the "good angle" you dont see the glue ...

when the polar is after the mirror, I always get this negative affect all around the screen with or with out residue ...

could this be a function of the triplet and the angle at which the light is hitting it ... the triplet is not very well aligned with the mirror .. I think the light off the mirror is hitting the triplet at an angle ..

why don't you just place the polarizer next to the LCD screen as originally placed?

I only bought the small one enough to cover the triplet. the one to cover the LCD is 75$ ...

can you adjust your mirror/triplet? It may be difficult but what choice do you have since you won't pony up for the larger polar.

And you are placing it behind the triplet.

I tried to put the polar before and after the triplet ... both give the same results. I am pretty sure it is the mirror.

Here is a list of placements and results (With glue residue cleaned off)
On LCD - GOOD
On Fresnel - GOOD
Between Fresnel and mirror (hanging in the air) - GOOD
On the mirror (taped on)- OK (seems to loose some contrast - I think!)

Between mirror and triplet (hanging in the air) - BAD
on the triplet (facing mirror) - BAD
On triplet (facing screen) - BAD

I don't understand whats the deal is with the mirror ... it is Al coated FS mirror. it is scratched up a little bit from abuse but not too bad to affect the image ... I am going to try my old mirror (if I can find it) which was too small ...

if it doesnt work than I'll flip the LCD so the original polar is facing the mirror and put the SHC polar close to the lamp and flip the image from the video card ...

but I would like to understand what is going on .. any thoughts ?

kind of obsolete plog

Short answer: Polarization is a strange, funky thing.

Long answer:
Dazzzla has the right idea, but it's apparently not the only culprit: "I think you should try to remove the rest of the glue residue. It looks to me as though it is acting as a retarder, slightly rotating the polarization so some of your screen is polarized at a different angle than the rest."

From your discription, it has to be your mirror that is retarding the light's polarization and creating the color effect. A birefringent protective coating on your FS mirror is probably acting as a wave plate or polarization retarder.

You can see the same color-changing effect looking backward through a circular polarizer filter for a camera at a polarized light source. This is because a circular polarizer filter is just a normal linear polarizer followed by a 1/4 wave plate.

Some (hopefully) useful links:
http://en.wikipedia.org/wiki/Filter_(photography)
http://en.wikipedia.org/wiki/Birefringence
http://en.wikipedia.org/wiki/Wave_plate
http://en.wikipedia.org/wiki/Polarization#Theory

Because it seems to act as a wave plate, you can likely remedy the problem by adding an appropriate wave plate (or compensator) before your polarizer.

It may be possibile to use ordinary cellophane:
http://individual.utoronto.ca/iizuka/research/cellophane.htm

However, you probably need something closer to a 1/4 wave plate. Cellophane is not a perfect 1/2 wave retarder, so you may be able to stack layers until you get the right effect. Experimentation is called for.

Another possible solution: Buy / borrow a circular polarizer camera filter and use it instead of your existing polarizing sheet. Make sure you point the threaded side (wave plate side) toward the LCD.

Good luck.

Yes you must have it before the mirror, the mirror will change the angle of the polarization, the best is to place next to lcd screen.

sorry i missed or forgot you said you had mirror in equation.

great links thanks ... I dont think I'll ever understand the concept that light travels in waves ... it was much easier when little photons were bouncing back and forth like billiards ...

I am definitely going to try the cellophane, if it works it will be quite a "mod" to the pj. reminds me of "mr. cellophane" in the movie Chicago ....