Water and oil anamorphic prisms
 

I have some different anamorphic plans, but the most realistic is the water and oil prisms I think.
It should look something like this to stretch vertically: http://s01.picshome.com/52a/water_prism.jpg
(edited note: with 35mm lens I meant 35mm adapter lens, so it could be any lens)

People use it and discuss it on the video projection board.
The first links explain the system:
http://www.diyaudio.com/forums/showt...=&pagenumber=1

Now I found out the same idea was first used in front of movie cameras in 1957 (see the second image):
http://www.widescreenmuseum.com/widescreen/wingup2.htm

I've made a very big lens last year, with normal glass so it has a lot of reflection.
I'll get non-reflective glass used for art and such, and make it as small as I can (to fit in front of the DOF adapter lens) to reduce the reflection.

I'm not sure why one of these lenses has to be filled with mineral oil.

Anyone interested in this project? It's not too difficult to make.

The only real downside to a waterprism is that it, well, contains water =D. It's not too big of a problem though if you do it correctly.

Those projector lenses they are making do look very interesting!

Some experimentation will be necessary, of course, to get the correct angles for the prisms. The great thing though is that prisms will allow you to fine tune the compression ratio without having to do an entire system redesign. The downside, as the one website points out, is that they can be rather large and cumbersome.

I think the reason you need mineral oil in one prism instead of water is that it has a different index of refraction. In essence, the oil bends the light to a different degree than water. This is probably necessary to correct the image back in line so it continues straight. This is just my guess though - I may be very wrong!

Aaron, you're probably right about the oil prism.

I think the first prism, closest to the camera lens, could be as small as 5x6 cm ( 2x2,4 inches)
The second lens about 7x8 cm (2,8x3,2 inches) So that's not too big(big enough though).
A wide angle lens behind it would mess everything up and it would require far bigger lenses I think.

I noticed that the original anamorphic lenses had the lenses on their sides (compared to my first design)
Like this: http://www.widescreenmuseum.com/wide...tar-prisms.jpg
or this one more clearly: http://www.widescreenmuseum.com/widescreen/c65lens2.jpg


This means that the image is stretched by collecting more view from the sides.
Here is a test shot:http://doublecam.250free.com/anam1.jpg

I just handheld everything and photographed through the lenses.
On the right side there is slight color aberration, maybe I'll use two water prisms.

I am working on the smaller rear water lens, made of two UV filters. Those filters have anti reflective coating, which is needed for such a big lens. They are different in size, which is explained in this image:
http://doublecam.250free.com/anamorph2.jpg

I have exactly measured and glued three plastics between the filters. Now I have to close the sides and make them waterproof. (epoxy glue)

The drawing is not exact at all, because I have to work out the angles just yet.

The front lens must be made of straight pieces of anti-reflective (museum) glass because of their size, 7 x 7 cm and 7 x 10 cm - (2,8 x 2,8 inch and 2,8 x 4 inch)

Very interesting Oscar! Do let us know how this works out!

Looking great Oscar - keep it up!

Almost done with the rear lens.
I got real high quality -anti reflective (coated) museum glass- today. As I am a painter and am acquainted to a framer, I got a left-over piece for free. I've already cut the pieces and glued the shape together with plastic sides, so I can come up with some tests in the coming days.

TESTS
 

I made the two water prisms. They must be lined up precisely, but I did a quick test that show one(first) problem: the more you look to the right, from the center of the image, the more it gets blurred by color aberration. To the left it is sharp.
Here are the results: http://doublecam.250free.com/

I think it's not too bad, but compared to the image shot without the lens, it obviously needs some work.

Looks nice :)

Is this the rear version? Keep up the interesting work!

No, front version. It's just too bad I don't have enough space in the adapter to make it a rear lens.
Aaron, do you know what could cause the color shifting to one side (one lens)?
I'll post a picture of the lens tomorrow. It's not as heavy as I thought it would be, but I'll need to make a rail system to mount it in front of the camera.

Hmm, I'm not entirely certain. I'd need to see how everything is setup before I can make any really useful comments. Test results are looking quite nice though :)

For those who are interested, here is a picture of the complete setup of the prisms: http://doublecam.250free.com/

I have to refine the angles a bit to get the same amount of squeezing on the left and right.

Note: so far, the costs are 0 euros (in American dollars: 0 $)

EDIT:
Aaron, I wonder if the small lenses, right next to the bigger ones in the original setup (like this picture: http://www.widescreenmuseum.com/wide...amorphoser.gif ) are to correct the color aberration.

That is some great stuff Oscar. Are you going to make the front Prism with Oil next?

I stick to two water lenses, because I'm getting more color displacement with the oil lens.

I just discovered that the color aberration seems to disappear when I change the angles something like this: http://s01.picshome.com/52a/angles.jpg

Just a quick drawing, they don't represent the exact angles.
The water prisms are both 30°


I don't really think it'll resolve it , because the compression won't be 16:9 anymore, but I'm looking for the reason for the color displacement in only one lens.

Oscar, yeah those extra prism pieces are there to help correct for color aberration. Might be something to try though I'm not sure it's worth the effort.

Setup looks nice. You might want to consider putting a normal spherical lens in front of the whole prism construction.

You're going to have to balance the compression ratio vs aberrations it looks like. What sort of compression are you getting from the setup with both at 30 degree angles?

Your right Aaron, this might be the balance you are talking about:
http://doublecam.250free.com/exact-angles.jpg (these are exact angles.)

I checked the aspect ratio of my homemade double camera thing (other tread) which is a bit more than 4:3. So the compression I get with these adjusted angles will be very close to 16:9 and the color aberration is very much reduced.

In the image you can see I meant 30° for the lenses themselves.
And Aaron, what would a normal spherical lens do? (by the way, thanks for your replies)

Ah! I understand what you mean now. 30 degree angled prisms.

Looks like a workable setup :). I'm definitely looking forward to seeing some more screen grabs and footage!

Generally, anamorphic cinema lenses house the prisms between lens elements of some sort. You can sort of see an image of a variable anamorhpic lens here (variable because it changes the orientation of the lenses with the turn of the knob):

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4791&item=5756817409&rd=1&ssPageName=WDVW

You can't really see the glass but if you look carefully there is a spherical piece of glass under which the prisms are held. I don't know if you will need one or not. It would be an interesting to test run. The lens, I believe, helps focus the light into the prism. You can change the field of view by changing the spherical glass etc.

I see, so maybe if you get the right spherical lenses, the water prisms could be much smaller if they are only to stretch the image collected (if this is the right term)by the front spherical lens.
Maybe this means that you'd have to focus the lenses apart from the normal lens? In my (current) case that's not necessary.

I'm definitely going to test a lot the coming days and post the results.

EDIT:
Oh, one more thing, maybe someone knows. It seems the lenses compress the image a bit more to the sides. Maybe there is a way, or better, a plug-in for after effects to stretch it more to the sides. Or less in the middle of course.

I had to make the small (round) lens over again and made a new one with straight pieces of museum-glass.
To begin testing, I made a rail system to mount the whole thing on.
The first two pictures on my site show my (very big) setup:

http://doublecam.250free.com/

The whole thing has to be covered with something, of course. Maybe some sunshades (flags?) too.

Oscar, what is the small silver thing that is hanging from the Lens? It looks like a silver pointer stick or something....

It's a (are, actually) bolt(s) attached to the rear lens to adjust the angle if needed.
In the top image, you can see another bolt in sleeve, this is to adjust the angle of the whole lens.
Maybe I'll 'tune' the angles (for color aberration) with the camera hooked up to a big monitor.

Here is a new test frame (anamorphic lens and double-cam):

http://doublecam.250free.com/anamorph6.jpg

I still have too much color aberration on the right side of the frame. It's very much visible (like a red blur)on the edge of the right can.
I hope I can get rid of this by adjusting the angle of the rear water lens.

Anamorphic people, I'd like you to check out my new test, because it's a compromise between the compression (16:9) and the color aberration. I've adjusted the angles of the lenses to the camera lens and came up with almost no color shifting (also meaning a slight blur all over)
But the aspect ratio is quite a bit less than 16:9.

Here's the frame grab:

http://doublecam.250free.com/beer.jpg

This is before I adjusted the lenses:

http://doublecam.250free.com/anamorph6.jpg



If the top link doesn't work, click on the first text on my site:
http://doublecam.250free.com/

Those look surprisingly good :) ! Great work!

Any chance you could post a shot with and without the adapter (of the same scene)? Just so I can get a good feel for what the compromises image wise are like?

What aspect ratio are you ending up with?

Impressed
 

Hey Oscar, sorry I haven't posted sooner. I just wanted to say that I'm impressed with your set up. The footage is coming along nicely. I wasn't really expecting much from the water/oil prism adapter, but I must say that I am very impressed with the images so far. I would love to try and make one of these sometime soon. Do you think you could get an even larger squeeze with different angles? I would love to get a compression to do 2.35:1, but I don't know how well it would look once uncompressed. Frankly I'd settle for anything at this point. Do you know about what compression you are getting now? I know you mentioned that to keep the image problems down you were squeezing slightly less than 16:9. Just out of curiosity, how are you figuring out how much to unsqueeze it? Playing it by ear or are you calculating it somehow?

Anyway keep up the good work and keep us posted!!

Thanks for the feedback.
I must do a test on the exact aspect ratio. I figured to shoot a grid of some kind. That also will show if the compression is equal all over, which seems like it, but at first, before correcting the angles, it compressed much more to the sides.

Keith, a compression of 2.35:1 would be great, but it has to come from thicker lenses. Maybe Aaron knows how to calculate this, but I'll also try to stack my older prototypes together and see what happens. If the compression is twice as high (with 4 lenses), the calculations would be easy.

I wouldn't mind trying to make a 2X squeeze prism like these, but I have no clue how to go about calculating the squeeze size, shape, angles of the prism. If anyone could tell me how to calculate these measurements, I'd be more than willing to take a stab at making something like this.

I've been thinking about trying to build one of these the past few days. I just was curious about something Oscar, do you think it would work with a wider lens such as a 24mm or so? Have you tried it with a wider lens or just the 50mm? I would think you might have to make the prisms longer/larger to cover the wider area that a shorter lens would cover. Do you think that would that be true?

They do something similar, but the other direction here.

www.panamorph.com

I have one for my projector and it's pretty cool. The version I have has solid acrylic lenses and has some color abberation and focusing problems because the optics are flat, while your camera and projector lenses are curved, causing focus and color abberations at the edges/corners.

Keith,
You're right, the lenses would have to be bigger to fit the view of a wide angle lens. Even big zoom lenses have a wide view. I'll test all this in the coming days.

Keep in mind that I made a real wide-screen lens, so the image (to the sides) on a 50mm lens is almost a 28mm view. This will compensate it a bit.




Good link Jacob. Can you see the angles (thickness) of the lenses on yours?

The amount of aberration has also to do with the fluid in the lens (and perhaps the acryl too), I found out that mineral oil has much more aberration than water.

EDIT:
Here is an image with excessive contrast and color saturation, to show it has minimal amount of color aberration on edges:
http://doublecam.250free.com/roofs.jpg

Oscar I've been trying to learn something about these prisms and whatnot and read through most of what I could in the diy audio site. I saw several posts mentioning 2.35:1 format from 4:3 source, but i never saw anyone who had made one succesfully so i guess if we ever want to try that we'll have to try it on our own. Not that anything we do around here is pretested though. All I could find about 2.35 was this post that I'll repost here incase you're interested...

"After some review of basic refraction principles, I made a spreadsheet for calculating prism angle and angle between two prism. You can adjust the refractive indice number as well.

As for 2.35:1 compression. If using glass prisms(30,60,90), the angle between the two prism is around 49 degrees."

If you're interested i think it was like post #308 or there about in the anamorphic thread on diy audio.

As for a wider lens. I do have 1 question. I know the adapter would be larger for shorter lens such as a 24mm or so, but if larger prisms were used and it would support a wider field of view such as a 24mm lens or so, would it also work with the longer lenses too? I guess my real question is would these prisms give the same compression/expansion to all lens that would fit behind them or would the compression vary because of the focal length of the lens?

Oscar,
Do you have any demensions on your current set up? What sizes are your prisms, etc?

http://doublecam.250free.com/WL5.jpg

The red numbers (sorry they are in cm) are the sizes for the glass of the front lens, the blue for the rear lens.

I think your right about the compression changing on the lens size. I doing a test with a zoom lens (80mm - 210 mm) right now, I'll let you know the results.

As far as my quick test can tell, there is no difference in compression between 50mm to 210mm.
Here is an example how the 210mm image fits exactly in the 80mm image. (You can also see the telelens gives dark edges on the left)

http://doublecam.250free.com/80-210mm.jpg

I've done the same test with 50mm and 80mm. This is great isn't it. I really thought it wouldn't work.

Yeah it seems like it's the same compression on both. So in theory if anyone made one large enough to fit the widest lens they have then it should work the same for all the lenses they own. That'd be very nice. Thanks for the measurements by they way. I'm also working on a wax "ground glass" for my adapter, but I would really like to start working on one of these soon. I just have to track down some anti reflective glass here in the US. By the way did you happen to notice the posts on the diyaudio forum about using glycerine in the prisms?

Darn, I spent all that time trying to find a cheap circle glass cutter and now I'm gonna have to get a straight one too.

Keith,
Another telephoto lens of mine with a smaler front( 5 cm) has clear sides, no vignetting. It's a 135mm lens.
Wide angle lenses will give more trouble of course.

You could make the lenses from round shapes if you want, it's just pretty hard to make the sides waterproof. I failed in this, but it'll look very nice, and save some space, if you get it right.

Yeah I think I'll stick with the flat panels for now until I get those to look right. A buddy of mine is looking to see if he still has the glass cutter he had, so I don't have to buy one right now. Are you using mineral oil for the oil prism and regular water in the water prism?

The title of this thread is confusing, because I changed both to water prisms along the way. Mineral oil has much more color aberration. This is probably a plus if it is used to correct the aberration of the rear lens, but only if everything is setup exactly right (all angles have to be changes changed with oil)

Don't use normal water, only distillated(is this the right word?) water (in the final version of the lens).

I just checked the thing on my 28mm lens, but that's too wide, like I though.