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Old March 7th, 2005, 05:35 PM   #1
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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.
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Old March 7th, 2005, 06:48 PM   #2
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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!
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Old March 7th, 2005, 07:08 PM   #3
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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.
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Old March 10th, 2005, 07:37 AM   #4
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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.
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Old March 14th, 2005, 06:35 PM   #5
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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)
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Old March 14th, 2005, 07:46 PM   #6
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Very interesting Oscar! Do let us know how this works out!
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Old March 14th, 2005, 09:32 PM   #7
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Looking great Oscar - keep it up!
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Old March 16th, 2005, 05:41 PM   #8
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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.
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Old March 18th, 2005, 07:01 PM   #9
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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.
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Old March 18th, 2005, 07:38 PM   #10
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Looks nice :)

Is this the rear version? Keep up the interesting work!
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Old March 18th, 2005, 07:47 PM   #11
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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.
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Old March 18th, 2005, 08:38 PM   #12
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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 :)
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Old March 19th, 2005, 11:29 AM   #13
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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.
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Old March 19th, 2005, 01:29 PM   #14
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That is some great stuff Oscar. Are you going to make the front Prism with Oil next?
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Old March 19th, 2005, 02:46 PM   #15
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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.
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