REALLY LARGE PRISMS

I am in the process of gathering quotes from different manufactures for really large prisms. Who would be interested and what would you be prepared to pay?

Mark

I just might be. Dont tell the wife.

less than $100?

Its about $100 just to get the prisms from the trophy maker. And since Mark's lenses are from australia (unless he can find a US source)- and they're larger than the regular ones as well- I think the price will be considerably more than $100

I also would be interested - I would like to see some results of the new lenses in action first tho. Would these prisms also be made of the same optic crystal, or are you looking into acrylic as well? If there isn't a significant difference in picture quality between the two materials for our much larger triplets - that could provide a sizable reduction in cost.

As far as cost... if it could be done for ~$150 that would be reasonable - but much more beyond that and I'd be considering upgrading my light source or some other aspect for that size of investment.

I think there would be alot more people interested if they knew what VC and HE was!

The only people looking at this thread are the ones who know - but if we could pass the knowledge of what they do to everybody - there would be a whole lot of interest.

just my 2c

kancerus - good point - I'll go back and try to add some more info into the first post to catch the eye of the newer readers.

The best page that I've found for explaining what an anamorphic lens does is this one:
Prismasonic Page

In our case, VC stands for vertical compression - this takes a tall picture and shrinks it in height. HE is horizontal expansion - this lens expands the picture in the width. The same two prisms can be used for either HE or VC (with two different orientations), provided that they are of sufficient size.

I think we need to get it stickied if we can too - because if we can get these lenses it would be a great benefit to all LL users.

A couple hundred, probably not more than $300, although that is right now, right this second, in a couple of months it could be more.

I have requested a quote for BK 7 with optic coating. I am also going to chase up a Persex version as well.

Stay tuned...

Mark

Mark - Sounds good, glad to hear that you're working to help the LL community as well as those with commercial units. Do you know if there will be seperate prices for the BK7 glass with or without optic coating? I'm not 100% positive, but I think that many of our triplets don't even have optic coating And the fresnels sure don't. I'm not sure if we'll know if it's necessary without a few tests.

Perhaps if you can do some experiments with the larger prisms that you currently have and kancerus' projector, it might be easier to determine if the extra cost of coating is worthwhile for our DIY projectors.

*edit*
I edited the 1st post in this thread, to try to better explain just what we're trying to do with the lenses. Feel free to PM me if I've missed something, or if it could be made clearer - I don't think we need to fill up the thread with that particular discussion.

I guess I would really have to know what the price possibilities are, if you can get large high quality prisms I will probably pony up for them even if they are expensive.

I don't know if this is how the powers at be came up with these aspect ratio standards or what but there is an interesting mathmatical correlation between the 3 most popular aspect ratios.

4/3 = 1.33:1
if you expand 4:3 by 133% (4 * 1.33) you get 5.32:3 which rounded off is basically 16:9
(5.32*3=15.96) and of course (3*3=9)

then if you take 16:9 or 1.78:1 and expand that by 1.33 you get 2.3674:1 very near to 2.35:1 cinemascope

these minor ratio differences 2.3674:1 vs 2.35:1 are not noticable to the human eye.
It seems to me that the relationships between these ratios are a bit too coincidental to be an accident.

I'll disagree slightly there. 2.35:1 is a common name or number to describe CinemaScope, but the actual AR of CinemaScope is 2.39:1. In video, that number is 2.37:1 (based on the math you've done above) and it is things like the MCA Unviversal "world" logos at the beginning of a film that will show you a difference between 2.35:1 and 2.37:1, where the globe is not quite "round" on the 2.35 screen but is round on the 2.37:1 screen - based of course that you have set the width by the screen's AR...

During a film, chances of seeing a true circle are limited, but watch films like Top Gun and Behind Enemy Lines (which are both an excellent example of the need for proper geometry)...

Mark

I did a little further research on this and it seems that the orginal Anamorphoscope lens developed in the late 1920's stretched a 1.33:1 image by a factor of 2 producing a 2.66:1 aspect ratio. The wide format didn't actally start being used until 1953. It seems that there was no master plan to develop a simple mathmatical relationship between 4:3, 16:9, and 2.35:1 (or other variations)

It is interesting that you mention that the actual film AR is 2.39:1, since I currently have a 2.35:1 aspect screen with the desktop resolution set to 1280x544 I notice that some transfers maintain that original aspect ratio. For example when I play Underworld evolution on my screen I get very small letter box strips on the top and bottom.

Sorry to get off topic, I am interested in the history and our relatively late breaking ability to produce the true cinema experience at home. I have to say that I am much happier with my CIH setup even without the use of an anamorphic lens, the experience is remarkable.

Any word on those big ass prisms?

Correct and the 2x stretch lenses are still used today with film...D-Cinenam I think uses 1.5x...And we use 1.33x for video...



In a real cinema, they use horizontally squeezed print (it looks tall and skinny at 50% of the proper geometry), a 2x stretch anamorphic lens, but also have a "gate plate" (not sure of the real term for this) that goes behind the primary lens. What it is for is to give the image a nice clean, sharp edge as it is brought into focus as the same time as the film image itself. Problem is, not all projectionist seem to know what the true AR for CinemaScope actually is, and I have seen all kinds of things ranging from 2.0:1 through to 2.40:1 with 2.20 being very common. In the private sector of the cinema arena, the projectionist actually make these plate them selves out of very thin metal. So when a film does differ to the "norm" chances are your not going to see it anyway, and in most cases, the real ends of the frame are cut off...



It kind if strange that we end up adopting all cinema (adapted for home none the less) technology for our HTs. It seems the image side however sadly lags by 50+ years...Audio seems to be much faster with Dolby Digital EX probably being the fasted technology ever adopted to the home (EX adapters were available with in 12 months of the cinema version)...

Nothing back on those prisms so far. The company I have requested my quote from have shut down for a week for Labour Day (I thought it was a day not a week?)

Mark

alright, you guys got my attention.....p_su, the silmar stuff you are talking about is like a table top resin, i have used something very similar to it for putting a flush mounted window in a 360, the stuff i used had a yellowish color to it, but the silmar is crystal clear....ill get a pic of it in action

edit: here's a link to some in action, click me, what he uses is actually silmar 249 and this stuff dries like lexan, and it is supposedly very easy to work with and pour without bubbles

edit#2: just bought some on ebay, found it CHEAP, only 2 left
BIMP

I hope someone has some success with this stuff soon without blowing too much ca$h...

Mark

well i hope to start on my lenses next weekend, and i was wanting to know what you guys think my angles should be with this stuff.....i am not looking to use this stuff insead of water, but rather to cast the wedges in some glass then pull them out......so should i go with 10* wedges, i would like to have my plans drawn for this project before it starts.....any help is greatly appreciated

thanks
BIMP

My personal photo is a piece of 'scope' film, from Superman Returns.

The scope prints offer better resolution than 'flat' prints, because the scope is not squished horizontally, but rather stretched to fill the entire square of film that it can occupy. Flat format films have black bars filling the space between the images.

When I was casting resin, I did managed to get 10 degree prisms to work OK, but could get them perfect. My probems were thermal - striations cured in the resin that prevented the image from focusing 100%.

Later I found crazy cracks where the resin was pulling away from the Perspex I was using as a mold, and finally I moved on to glass, but then had problems with shrinkage, which caused my prisms to crack. All fun and games, but got a little expensive towards the end for DIY. I am so glad the crystal prisms were dscovered.

Hopefully the large prisms will be affordable...

Mark

well i think that the the molded prisms are all a matter of mixing ratios, and how hard they get.......i want to mix mine to dry very slowly, they will be less brittle and less likely to crack and break, of course if that does happen i will try some clear fiberlass resin that i saw on ebay, but the only problem with that is something tells me that fiberlass resing will be cloudy and not suitable for this application........i read a lot of the diy audio forums thread on diy anamorphic lenses, it has to be just a matter of finding that magic resin....its out there and i will not give up until it is found, that would be the ultimate way to produce "cheap" lenses that anyone could afford

i think the trick is going to be to just get them to cure as slow as possible, buy i will try a fast cure and a slow cure and i have a few other things i would like to try, but as far as anyone knows has anyone used the silmar 249 yet?

BIMP

As far as what I am willing to spend, that has changed a bit. I am willing to do whatever it takes to make a HE lens. I have decided to build a new vertical fold projector with the beseler lens so the trophy prizms wil not cut it. I need the big dogs.

The thing is that the depth of the room will not allow me to project a full frame 2.35:1 image without the HE lens when I switch to the beseler triplet. I need the HE lens to expand the 16:9 image from 103" to 136". I have 16' 3" from the screen to the back wall wich will just allow me to throw a 16:9 image to the proper height of the screen (58")

i know if i can get the silmar to pour right and not crack and bust, i will make several and sell them CHEAP, not so much to make profit, i want to get lenses into the hands of as many people as i can (that is just more people to test them and see what setup works best), then we all can really start to tweak on these things!!!!! i so ready to get started

BIMP

Sounds good, I'll pay your expenses if you can send me a pair to test

definately, all i ask for is what i have in them, which i dont know yet how far my supplies are going to go, or if its even gonna work but if all goes well i will let everyone know, and then we can start figuring prices....but i will not try to make a profit on them...............yet

BIMP

If I am doing my maths correctly, your TR (Throw Ratio) should be 16' 3" or 195" (projection distance) divided by 94.34" (16:9 image width based on the 53" image height) = 2.0.

Is this correct?

If so, the 170mm x 140mm prisms I use in the "Aussiemorphic Lens" will work with a TR of just 1.3:1 and get way better at or above 2.0:1...

HERE is the lens in action with the BenQ 8720 at a TR of about 1.9 or 2.0, and HERE is the lens at work at about TR of 2.2 or 2.3:1. I only wish I had kept the photos in the first link full file size now...

Mark

nope that is not quite right.
the math is good but the numbers are wrong
you see it is 16'3" from screen to rear wall. PJ will go in front of the wall naturally. Anyhow the height is 58" and the width is 103" and the throw is 160.5 inches.

so projection distance 160.5 divided by image width 103 = 1.56:1
I thought that there was talk of a 100mm lens having a larger initial light cone though due to it's size. The LL standard is 60mm and it has a very rapidly expanding light cone due to it's 1:1 throw ratio. What size in mm is the diamiter of your commercial PJ lens? You are making me want to throw down for trophy prisms to try them out.

Have you got a set of those prisms already?

The BenQ lens is about 100mm, but the TR is around 2.0:1

My Sony lens is about 60mm but the TR is just 1.3:1 and if I zoom the image to the largest size, that number falls to 1.1:1, so at this stage I can not see why a 1.5:1 TR would not work...

Mark

Nope I don't have the tropy prisms but I am going to buy them after the last factoids you told me about.

The 6" x 8" might be the go...

Mark

What do you mean? there is a 6" x 7.5"
what do you mean "might be the go..."

There is different sizes in the states vs the ones we have here vs the ones I've had custom made for my lens...

Might be the go, as in it would pay to get the largest size which I thought was 6" x 8". Half an inch should not matter too much...

Mark

That is what I thought you meant
My landlord for office space is the owner of www.adplanet.net so he sells this type of thing. I am going to call the company glassgraphics.com tomorrow and pretend I am part of that company and order some blanks. I should be able to get the cheapest price that way since it is direct from the manufacturer. What is even cooler is that the company is based in NH and I am in VT. They are like a 1 hour drive from me. I might even be able to get my hands on them this week.

Keep us all updated...

Mark

EDIT: order is in, I will probably get them tomorrow or Friday.

EDIT 2: I was just thinking about the eVo projector, I am recomending one to a my office landlord for a cheap theater setup. He is aware of what I am up to with the trophy prisms as he placed the order for me. Anyway what is the throw ratio on that beastie, do you guys think the trophy prisms could be used to anamorph that PJ in a CIH setup (HE lens)?

eVo? Do you have a link?

Mark

LOL, Mark I know you are a smart guy but have you been living under a rock for the past 6 months? http://www.lumenlab.com !
the eVo
LL's super low budget PJ!

Sorry, must have been but I did click on the link the other day.

I bought my projector in fear of not been able to DIY that part

Mark

Um and the eVo is not a DIY projector either,
I did a little research and it appears that the eVo is about 1.25:1
So it might work for HE with the trophy prisms since you said that your lens works with throws of 1.3:1 and the trophy prisms are slightly larger than your lens.

ATTENTION EVO OWNERS, HELP THE ANAMORPH CAUSE!!!
I can get prism blanks direct from the manufacturer and I will take paypal and ship worldwide. Contact me or post here if you are interested!

I can probly get a pair of prisms anywhere in the world for less that $100 USD

I thought I would add some info about my test design for the anamorphic lens.
I had my friend, who is a carpenter turned DIY PJ enthusiast, cut me a couple 12" x 12" plywood squares and drill quarter inch holes in the corners with a drill press. I am picking up 4x 8" carrage bolts tomorrow with washers and wing nuts. The idea is to just clamp the prisms in place by tightening down the wing nuts. It is pretty similar to the picks that p_su posted at the begining of this thread.

It should work pretty well for a test run and give me an idea of what the actual measurements should be for the final design. I hope I get my prisms tomorrow, fingers crossed.

Hey everybody,

Got some good news - just tried marks anamorphic lenses on both the pro and the standard LL lens.

They both work with HE no problem - VC on the pro works but not on the Standard.

With the pro - there was very little pin cushioning and it looked great.

With the Standard lens the pin cushioning was there - mainly cause its such a short throw - but nothing a majorly curved screen cant fix hehe.

I am buying a couple as soon as he gets them in stock and I will test them further!

what LCD do you have in your Standard setup and what LCD do you have in your pro setup?
The size of the lcd will affect the size initial light cone! E.G. the 10.6 with the standard lens would produce a longer throw than the 15.4 with the standard lens.

I am not getting the prisms until Monday, %^@#*&*@#
I ordered on Wednesday and the company promptly did nothing at all untill I called them just now.

This is great news! However I was thinking of using a Beseler Opaque Projector Triplet in my new build, I think there may be some prolems with that because I just rembered seing pictures of it and it being about the same size as a 100 cd cake box which would make the diameter of the lens around 130mm, can anyone confirm the diameter of the Beseler lens?

I have a 15" in my standard setup and a 17" in my pro setup (That will be changing to a 15.4" once I get my Kontron controller working!)

I think it is more to do with TR at this stage...

Mark

i am getting a 18"ef opaque lens also, like the beseler......and i think you are correct on the size, i hate to think how big an anamorphic lens is going to have to be for these things....no worries, i can make any size i need , that is if all goes well.....i ordered my resin over a week ago and it still isnt here, oh well

we will get something to work

BIMP

if you look at marks above post he is saying that the throw ratio is a bigger factor than the lens diamiter, the beseler throw with a 15.4" LCD seems to be about 1.5:1 according to my calculations. Based on the rest of the experiments in this tread I would deduce that you could make a HE lens for the beseller but probably not a VC lens. It also depends on LCD size as that affects the TR, a larger LCD will produce a bigger picture at a longer distance than a smaller LCD will at the same distance with the same lens, so I bet you would have no problems using an anamorphic lens with any triplet in either VC or HE if you used the 10.6" LCD.

EDIT I calculate that the 10.6 LCD has a throw of 1.5:1 when paired with the standard LL triplet, can a 10.6 owner confirm that, (this was calculated based on unsplit optics)
I figure that the split optics approach would give a slightly shorter thow because of the greater magnification provided by having the front fresnel in front of the LCD.


I am working on putting together a design for my new setup which is interesting because much of the design is based on using the HE lens to achive a larger image on 2.35:1 content with the pro lens. There are a lot of factors in the design process but for me it comes down to 2 points, the size of the image you want and the room that you have to work with. These points are what drove me to use the standard triplet in my first build. I wanted a huge screen, 11' wide in a room that is only about 16.5' deep. My solution was shorter throw. Now with the Anamorphic lens as a factor in the design I only need to produce a 9' wide 16:9 projection with a long throw lens to achive my goal. My point is that this is another significant advantage to the DIY builder. Using an anamorphic HE lens a larger higher resolution image can be produce in a room with limited dimensions. Thanks to the Anamorphic lens I will be able to upgrade to the pro lens without reducing my projected image size.


EDIT AGAIN:
I should actually be getting my trophy prisms today, I am excited

Got my prisms today and they work, Massive inverted pincusioning.
I now am in the market for a pro lens kit in a big way.

With the standard lens? Yeah I think its just way too close to the screen to be able to do it. Mark was telling me about another way to do anamorphic - with a curved mirror or something? It is a pretty big way of doing it but it has no CA and I think no pin cushioning.

I thought briefly about the curved mirror idea and I think it could work. Here is my stab at a possible solution...

Take 3M ESR film (98.2% reflectivity), or some other reflective polymer film and glue it uniformily to a thin flexible hardboard. Have the corners clamped and adjustible somehow (perhaps with threaded rod?) so you can control the bend of the hardboard and the resultant curve of the ESR. Place this apparatus after the triplet like a typical folded design, and adjust the corners of the hardboard until you get the curve (and hence image compression) that works best.