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Old April 2nd, 2005, 03:00 PM   #31
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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.
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Old April 2nd, 2005, 06:24 PM   #32
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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
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Old April 2nd, 2005, 07:05 PM   #33
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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?
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Old April 2nd, 2005, 08:04 PM   #34
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Oscar,
Do you have any demensions on your current set up? What sizes are your prisms, etc?
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Old April 3rd, 2005, 07:08 AM   #35
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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.
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Old April 3rd, 2005, 08:49 AM   #36
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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.
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Old April 3rd, 2005, 01:05 PM   #37
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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.
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Old April 3rd, 2005, 02:25 PM   #38
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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.
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Old April 3rd, 2005, 03:34 PM   #39
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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?
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Old April 3rd, 2005, 05:26 PM   #40
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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.
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Old April 4th, 2005, 03:33 PM   #41
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Yeah that makes sense with the distilled water. I just picked up some cheap window glass for a prototype and a glass cutter today. I'm gonna start working on some stuff tonight. What did you use for the tops and 3rd side? I noticed you pliers in the one pic, are those the type to actually work with glass or are they regular pliers? The place I went didn't have the type for glass working.

Eventually once i get an okay version of the 16:9, i'd like to try and 2.35:1 ratio. Do you think to get a wider image you could just decrease the angles on the prisms? Say to like 20 or 25 degrees (instead of 30 degrees)maybe?

Also you said that the 28mm lens was too wide. How much larger do you think the adapter would ahev to be to fit that sized lens? I mean would it have to be twice the size? less?

Okay that's enough questions.
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Old April 4th, 2005, 03:34 PM   #42
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Oops

Sorry 1 more question. When you unsqueeze the footage, are you just doing it by eye or are you using some way to make sure you're desqueezing enough or too much?
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Old April 4th, 2005, 06:15 PM   #43
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Keith,
I made the other pieces from the clear side of CD jewel cases, grind it with sand paper to lose the reflection and paint it black on the outside when everything is finished.I always glue everything with (a lot of) 30min epoxy and when I'm not sure it's waterproof I put some kind of black roof adhesive on it.

To test the sizes the lenses should have, try holding some cardboard in front of the lens and note when it gets in and out of view. The farthest point will be about 10 cm from the front of the lens. I'll test this on my 28mm lens too, because I don't know.
If you make thicker lenses (more than 30) and we compare compressions, we might come up with a calculation of the compression.


I'm not sure which pic you mean, but they must be regular pliers. I break the glass on the ruler itself (put the cutting line on the edge of the ruler after you cut it, and break it by pressing it with your hands. Also, don't push too hard when cutting and use some white spirit on the cutter.)


On one test I unsqueezed the footage on top af a shot without the lens, so I could check exactly what it should be.
Hope it works out for you, let me know!
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Old April 4th, 2005, 06:58 PM   #44
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Step 1

Okay got the stuff set up on my work bench and cut out some pieces of glass. I need to figure out what to use as oil. I wonder if something like WD-40 would work or if you should use something special.

I based my calculations on your prisms Oscar. I just enlarged the size slightly. I think it's only about 25% larger maybe. I figured I'd try to see if I could make it fit a wider lens.

I'm also going to cut another set possible once I see how this works to test alternative angles to try for 2.35:1 or something close. 2 questions about that... 1 to make the view wider the angle of the prisms should be smaller (20-25 degrees maybe) or am I thinking wrong? Also do you think I should make the panels longer side to side to account for the wider view? I mean the angles are the most important part correct? Even if I made the sides longer it woudn't hurt anything would it?

There are some pics of my progress so far at the bottom of the page posted below if you want to check them out.

http://www.twistedinsomniac.com/mini35/
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Old April 4th, 2005, 07:42 PM   #45
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Perfect! I had the exact same thing set up a week ago.(my grand piano was the work bench though)

The best, most quick way to seal it is definitely epoxy glue. Tape or hot-glue will be leaking in a few seconds. I put the top (non-angled) plastic part last and flushed the triangle box just before that. This part has to have a small hole on the highest corner to give the smallest bubble of air as possible when filled with water.

I didn't use oil, but water for both. If you want to use oil (for the front lens) maybe WD40 is too aggressive, I used some sort of cheap furniture mineral oil for a test lens.

About the angles, to give higher compression the lenses have to have a bigger angle, like 40 degrees. I mean the lenses themselves.
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