AVS Forum banner

Just got my French Prisms

108K views 334 replies 51 participants last post by  thatsmekid 
#1 ·
A while back there was a group buy hosted by Skhattane.


Unfortunately that group buy was not authorised by AVS and was therefore blocked and deleted from the site. Some of us though, did get in on the deal especially since it was posted for some time and seemed like a legit buy.


Anyways Skhattane did inform us that it would take a few months for the prisms made of BK7 glass and AR coated would take a few months to produce and then a couple of weeks to ship. It took a little while longer than expected and I was somewhat concerned wether I would ever get the prisms. I am happy to report that the prisms have made it here a'ok.


They were extremely well packed and shipped US priority mail. They actually came from PA. I only have opened one of the prisms which were carefully wrapped and it is in perfect order. I carefully held it up to look thru and see how the clarity appears and I can say that it is amazingly clear. Now I just need to work on an enclosure for them but it will probably be some time before I get to this as I am still working on my room. I temporarily set up my projector though for my son's b-day and if I can safely place them in front of the projector to see how they work I'll probably do that.


If anyone else is waiting for theirs they are on their way.


Thanks Skhattane maybe next time you can work with AVS to make it a smoother event.
 
See less See more
#3 ·
What a cur incidences, I was just thinking to my self (befor I looked into avs) about maybe how I could fallen for such a scamed and, then I tuned into avs and the first thread I looked at was yours. That makes me feel better.


Mine should comming soon to Hawaii. I should now be thinking about my containment box too. Please feel free to share ideas.


I have metel milling machines. I can shape metal to any design. If someone could come up with a good drawings I could make one for the contribetor and me.


But most of all Thanks for the INFO.
 
#4 ·
cool I am in your group so maybe soon for me I hope
 
#5 ·
Shipping in the US was 5 bucks. The place where they were ordered and shipped from ships anything to the US for 5 bucks. Not sure about Canada or HI but it should have been part of the payment.


I grabbed copies of pics from the original thread or from the french site (not sure which) of a couple of enclosures.


 
#6 ·
and


This enclosure is made of pexiglass it appears. The last pic is a diagram for the cuts used. The prisms are smaller than you might think so you wanna wait till you get them before committing to anything.


 
#7 ·
Then there's a simple solution like:


Sorry no photo account.


 
#8 ·
I wanted to add these pics because they illustrates how to a create case which allows for a passthrough mode with dimensions. Again I don't take credit for any of these they are pics from the French site. Thanks goes to them they've done a lot of hard work.


 
#9 ·
Yes they have done their home work, but I do have to question their prisms angles, especially the rear prism. Based on the diagrams, I believe that the image will not provide a true symmetrical stretch, as the front prisms essentially stretched the left side whist the rear prisms essentially stretches the right side.


Did anyone them actually build the unit with a pass through?


Mark
 
#11 ·
The largest prism face is 110mm x 70mm or about 4.5" x 2.75" at 20 degrees, so pretty small...


Mark
 
#12 ·
i'm still waiting for mine to show up in Sydney. i've been regularly checking updates on the french site w/babelfish and haven't worried that i'd been scammed. i plan to make a simple sliding enclosure such as skhattane posted. cant wait!
 
#13 ·

Quote:
Originally Posted by CAVX /forum/post/0


Yes they have done their home work, but I do have to question their prisms angles, especially the rear prism. Based on the diagrams, I believe that the image will not provide a true symmetrical stretch, as the front prisms essentially stretched the right left side whist the rear prisms essentially stretches the right side.


Did anyone them actually build the unit with a pass through?


Mark

I wondered about the prism angle when I saw the rear one more straight and the front one at more of an angle on some of the pics I saw, like one of the diagrams above. I did see a setup on the french site with a picture flashing back and forth of an enclosure switching from pass to strech. It had some sort of binding mechanism which only allowed for the prisms to turn so far, If I find it I'll link to it.


When I held up the prism to look through it did shift everything over so I am confident it will work.
 
#14 ·

Quote:
Originally Posted by 1Sharpdog /forum/post/0


I am now worried about the size of these prisms. What are their dimensions? It looks like they are only 2.5" high. I don't think that they are large enough for my w9000. Does anyone now if they will work?


Luke


The prisms are small compared to others. Most of us asked if the prisms would work with a particular projector because of this, and if Skhattane knew of someone that had previously used it he would tell us so. Since you have one of the newer 1080P projectors their might not have been someone who tried it out.


You can try the paper test to see how large an image is being projected on to a white sheet of paper 6-8" away from the projector. If it is about 4" you should be ok. Good luck.
 
#15 ·

Quote:
Originally Posted by voicecoils /forum/post/0


plan to make a simple sliding enclosure such as skhattane posted.

I liked his enclosure as well, simple top and bottom with a bolt at each corner. I wondered if the sides being open though would cause a flury of reflections even though the prisms are coated. We shall see soon enough
 
#16 ·

Quote:
Originally Posted by oman321 /forum/post/0


I wondered about the prism angle when I saw the rear one more straight and the front one at more of an angle on some of the pics I saw, like one of the diagrams above. I did see a setup on the french site with a picture flashing back and forth of an enclosure switching from pass to strech. It had some sort of binding mechanism which only allowed for the prisms to turn so far, If I find it I'll link to it.


When I held up the prism to look through it did shift everything over so I am confident it will work.


My prisms are a bit less at around 14 degrees, but what I found when using two of the same angle (not any different from what you guys will doing) is that if you only moved the front prism, that only the left side will stretch. Yes you can get a full stretch by then turning the lens, but the stretch will not be symmetrical...


Mark
 
#17 ·
 http://www.homecinema-fr.com/forum/v...asc&start=3030


This is the link to the French site with the rotating enclosure. I thought they used these prisms to make it, but it appears to be of the home brew variety. It's a little past half way down after the first enclosure.


Mark, the first pic in post #8 shows the prisms flat against each other, when shifted for stretch the opposite side becomes flat against the projector lens. Not sure of the properties of these prisms but it will be fun to see how they come together. I almost wish I had ordered a spare set for testing, now I have to be extremely careful.
 
#18 ·
Got mine today!!!! In perfect condition. Thanks SAM, where-ever you are...
 
#19 ·

Quote:
Originally Posted by oman321 /forum/post/0

http://www.homecinema-fr.com/forum/v...asc&start=3030


This is the link to the French site with the rotating enclosure. I thought they used these prisms to make it, but it appears to be of the home brew variety. It's a little past half way down after the first enclosure.


Mark, the first pic in post #8 shows the prisms flat against each other, when shifted for stretch the opposite side becomes flat against the projector lens. Not sure of the properties of these prisms but it will be fun to see how they come together. I almost wish I had ordered a spare set for testing, now I have to be extremely careful.

A thicker prism (ie 20 degrees) won't need as much angle as a thinner prism, but I think that you will find that the angles still need to be the same off the centre axis for both prisms. This has been well documented on both this site as well diyaudio.


It would change if the prisms used different angles, or were made from different materials, but in this case, both are BK7 and both have a 20 degree angle...


Mark
 
#20 ·
That's good news T_MINTON,


Are you ready to go with your set up? If you are, post some pics of what you end up doing.
 
#21 ·

Quote:
Originally Posted by T_MINTON /forum/post/0


Got mine today!!!! In perfect condition. Thanks SAM, where-ever you are...

I also got mine. I have not unpacked them. I hope they are ok.

But the concern is if they would work. They seem awfully small and they are

not identical as the package looks like and as CAVX points out that

could be a problem.


Anyway will wait and see if $126 works or if it is down the drain already.


Most likely I will sell one pair or both the pairs and will post a message.


If the mods are irresponsible enough to delete this thread or this post then

check videogon or ebay.
 
#22 ·

Quote:
Originally Posted by Mupi /forum/post/0


They seem awfully small and they are

not identical as the package looks like and as CAVX points out that

could be a problem.

No, they have the same angles, but the prisms' shapes are specified as front and rear, where the larger prism is the front...


Mark
 
#23 ·
I don't believe they are too small. It will be a while before I get set up...I may need some help from MARK about throw distance for these. I have an NEC HT 1000.Older , but stil a great picture. I am sure I need to move PJ closer to screen or I will be way too big. Plus I am gone next week to Gatlinburg and BRISTOL race.
 
#24 ·

Quote:
Originally Posted by T_MINTON /forum/post/0


I may need some help from MARK

I don't know how much help I'll be - I don't own a pair of these. You need to work off the smallest image size possible within the zoom range...


Mark
 
#25 ·
Curious Mark,


Does that mean start with the smallest image possible and go up from there? I understood for CIH that one would start with their preferred 16:9 image and then place the prism's in front to get 2:35.


I will most likely have to start/go with my smallest image size since i'm projecting from about 15-16' and have to account for speaker placement and masking which I will have recess to the sides or above.


So much to do, such little time.
 
#26 ·

Quote:
Originally Posted by oman321 /forum/post/0


Curious Mark,


Does that mean start with the smallest image possible and go up from there? I understood for CIH that one would start with their preferred 16:9 image and then place the prism's in front to get 2:35.

These prisms are small, so your TR is going to have to be quite high even though Sam did make a post in the now deleted thread that 1.4:1 would work, I seriously doubt that. I'm at 1.3:1 and the image in the front prism of my lens is just under the full width of 170mm, so no chance that 110mm is going to work on my system...

Quote:
I will most likely have to start/go with my smallest image size since i'm projecting from about 15-16' and have to account for speaker placement and masking which I will have recess to the sides or above.


So much to do, such little time.

I suggest to start with the smallest image size, then move the projector back if you have the room and still want a bigger image. For so long, people have relied on the zoom on the projector for more light and larger image size. That is OK when there is no anamorphic lens involved, but now you have to fit that light inside a very small area and not clip (vignette) the beam...


Mark
 
Top