Anyone considering selling their AR-coated prisms?

[Steve Scherrer]

I kind of missed the whole AR-coated prism buys, which were much cheaper because of the group buys. Anyone have a set they are considering parting with? PM me. Thanks.

[Mupi]

I kind of missed the whole AR-coated prism buys, which were much cheaper because of the group buys. Anyone have a set they are considering parting with? PM me. Thanks.

Yes I am. but I am not sure if you are looking for the French prism or the one
that was obtained from Crystal Factory in CA.

I have 2 pairs of the French prisms. I had mentioned about this in the other
thread. One is my pair and the other is my friend's. He has not taken it yet or rather I have not given it to him yet :-)

Most likely he will let me sell it as he knows that my experience has not been very positive (pl. read my posts in the other thread) . As I also mentioned, one of the prisms has a small chip at the corner but it does not affect the performance. There are others in that thread who also said they had chips. May be due to shipping. I still have not opened my friend's pair. If he agrees to let me sell his pair then I will open his pair to check if they are ok.

I offered to sell mine for $110 and I also offered to pay S&H if it is less than some 15 bucks (only within USA). If S&H is more then I will pay 50% of S&H.

[CAVX]

I am curious Mupi, what level of performance were you expecting at $120?

Mark

[Mupi]

well from what people were talking here about the posts in the
Frech forum, it looked like the prisms were delivering stellar picture.

Also the screen shots from guys who used the coated crystal
factory prisms looked very impressive.

But I could not get the same type of image. If I zoom all the
way down (i.e zero zoom) the picture was a lot better but it was way too small.
With full zoom, the prisms didnt do very well. I cant move the projector
any farther.

So I have decided to sell them. Nope I didnt expect them to perform
like the pro lenses :-) As I mentioned in one of my posts in the other
thread there are reasons why the pro lenses are expensive. If they have to
make a lens such that when you put it in the path of the light beam it does not
degrade the picture quality, it has got to be expensive!

I am not going to spend any more money on DIY prisms/lenses. I am a picky
guy but at the same time I also dont want to spend $2000 on a lens that
most likely will satisfy me :-)

If no one buys my prisms I would just play with them during Thanksgiving
or X-mas break to see if I can get a good placement and a good image.

I would like to get rid of at least one of the 2 pairs I have.

The other pair does not have any chips in case
people are concerned about the chips.

[CAVX]

Given that you have four prisms to play with, have you tried turning two 90 degrees and leave the other two horizontal? It is possible (though I admit the results are unknown) that you may be able to create a bit of zoom (vertically) to help with your image size. If this works, the lens will no longer be CIH, but may help out.

Might be worth a try...

Mark

[Mupi]

Nope. Havent tried that. It may be hard to make an enclosure for 4 prisms. Besides I really want to keep CIH.

[Mupi]

PRISM DIMENSIONS:

BTW Here are the prism dimensions as some of you had asked via PM

The first lens (one closer to the projector) is shorter than the second.
Both are of same height and angle. I dont know the angle off hand. I have
to get a calculator and compute it.

First Lens: Length 3 3/8 inch (this is the length of the slanted face)
Height 2 3/4 inch

Second Lens: Length 4 2/8 inch (length of slanted face)
Height 2 3/4 inch

[Lindahl]

But I could not get the same type of image. If I zoom all the way down (i.e zero zoom) the picture was a lot better but it was way too small. With full zoom, the prisms didnt do very well. I cant move the projector any farther.

So I have decided to sell them. Nope I didnt expect them to perform
like the pro lenses :-) As I mentioned in one of my posts in the other
thread there are reasons why the pro lenses are expensive. If they have to
make a lens such that when you put it in the path of the light beam it does not degrade the picture quality, it has got to be expensive!

I am not going to spend any more money on DIY prisms/lenses. I am a picky
guy but at the same time I also dont want to spend $2000 on a lens that
most likely will satisfy me :-)

Even pro lenses have serious geometric problems at short throw distances - it's the nature of bending light, not the nature of the glass/optics. The expensive pro lenses improve on CA (4 prisms) and focus (higher quality glass and an astigmatism correction element). If I understood your other posts correctly, you couldn't live with the geometric distortion? If so, CIH just won't work for you, even with the $6000 Isco III.

[surplusshed]

Hello Everybody!!!
The prisms you are all refering to where made by us - Surplus Shed

We now have them available on our website and will be stocking them on a regular basis.

Here's the link:

http://www.surplusshed.com/pages/item/l9113d.html

We only have 8 in stock right now but are having more made and they will arrive in about one month.

Please let us know if everything is described properly or if we should add anything to our desription.

Thanks!
Brent Gilson
Surplus Shed

[CAVX]

Brent,

When using a DLP projector to play a movie there are black bars on the top and bottom (widescreen), when positioned correctly, these prisms remove the black bars by stretching/correcting the image with no distortion.

This come from your website is totally inaccurate. The projector removes the black bars through a process we shall simply call "scaling". As a result, the geometry is affected (the image appears tall and thin as if vertically stretched). When the prisms are placed in the light path (with correct alignment) they optically restores the geometry through horizontal expansion, allowing the projection of films in cinema scope the way they were meant to be seen...

Mark

[Riblet]

Looks like he made some corrections on the website. :)

[putz2k1]

Does anyone know if these would work with an infocus IN72 at near minimum zoom?

[RandyFreeman]

The Infocus IN72 has a recessed lens and a curved front case. This makes it harder to get the front prism close to the lens. One thing that helps is to cut the housing that you build for the prisms at an angle so that it can sit closer to the projector. Just watch that you don't block the front air vent on the projector.

I moved my IN72 as far back from the screen as possible to keep the angle of the beam as small as possible. I use the prisms to vertically compress a 16:9 image to 2.35. In this vertical compression mode I was barely able to fit the image in the lens with the projector set to minimum zoom. Using the same prisms for a horizontal expansion lens there is more room to fit a bigger image through the 5"x7" prisms. I don't know if horizontal expansion lens can accommodate a fully zoomed out image. My guess is that it can, but that is only a guess.

Randy

[CAVX]

Using the same prisms for a horizontal expansion lens there is more room to fit a bigger image through the 5"x7" prisms.

Problem is I think the prisms he is referring to are the Surplus Shed prisms (AKA the French Prisms) which are about 2.75" x 4.33", so very small.

I am still puzzled as to why they choose such a small prism. A prism lenses will be bigger than a cylindrical due to the bulkiness of the prisms, so really restricts your usage in trying to make such a small prismatic lens...

Mark

[RandyFreeman]

I would certainly like to be able to use the French prisms because the anamorphic lens would be very small. But the small prisms probably won't work on most projectors, like the Infocus IN72, that have recessed lenses. At least not a projector with a recessed lens, that is positioned close to the screen, with the lens zoomed out. Somebody, please correct me if I'm wrong.

Randy

[CAVX]

Your exactly right :) The beam angles increase too fast with short throw ratios for that size prism...

Mark

[Anthony1]

Would I be able to use one of those French Prisms with my MitsHD1000u projector? I'm not sure if the MitsHD1000u has a recessed lens and a curved front case, as was explained with the IN72. I'm using a pretty long throw, about 18 feet, and zero zoom. The MitsHD1000u doesn't have the vertical stretch, but I do have a Optoma HD3000 scaler.

[CAVX]

Would I be able to use one of those French Prisms with my MitsHD1000u projector?

Not too sure about the TR with that projector, but you need a pair of prisms to make the basic anamorphic lens...

Mark

[Anthony1]

Not too sure about the TR with that projector, but you need a pair of prisms to make the basic anamorphic lens...

Mark



TR = ?

[CAVX]

TR = ?

TR = Throw Ratio where if it is too short, the beams expand to quick requiring a much larger adaptor...

Mark