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Old June 23rd, 2005, 05:23 PM   #1
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prism that flips vertical

I reacently dismantled a pair of old binoculars, and inside I found two prisms that flips everything vertically. It doesn't flip horisontaly, but since I got two, I might be able to flip vertical too. Has anyone tryed this before? Do you think I loose too much fstops?

Here is a picture of it. (bad camera, sorry). I'll take a better one later.

http://arez.vestlan.com/dof/prism.jpg
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Old June 23rd, 2005, 08:23 PM   #2
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i have tried an erecting prism, and it works... but you lose more light, and you have to adjust focus somewhere, just not sure where...
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Old June 24th, 2005, 12:31 PM   #3
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Im of to Denmark for 10 days now. But when i come back, i can do some tests and show you guys the results.

Last edited by Rune Hals; June 24th, 2005 at 12:47 PM.
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Old June 24th, 2005, 01:55 PM   #4
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Quote:
Originally Posted by Rune Hals
Im of to Denmark for 10 days now. But when i come back, i can do some tests and show you guys the results.
If you rotate them against each other you will see it flips both ways.
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Old June 24th, 2005, 02:45 PM   #5
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Jonathan, have you tried this method in the G35 yet? Also, in your experiments in developing the G35, did you find any places that sell boss screen type equiptment for cheap? I found something called hama and something called hudson photographic, but both are expensive and seem to be low quality options.
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Old June 24th, 2005, 04:51 PM   #6
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The prism that you have in that pic appears to be a Dove Prism, which only corrects one way. I don't know why a Dove Prism would be in binoculars though. I've only know Roof Prisms to be in there.

As for prisms, roof prisms are the only ones that will flip (left to right) and invert the image. It's what I'm using in my design which will have no ground glass....only optics. However, the more glass and optics you go thru, the more light you lose. So, it would be wise to use medium format lenses. I'm sure you could get by with 35mm lenses, but the larger the lens, the better. You collect more light from the lens which is just better all around. It's the same idea for telescopes....the larger the diameter, the more light you can collect. I'm making mine to accept Mamiya 645 lenses as well as Pentax P-mount 67 lenses (the larger, medium format).

Court
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Old June 24th, 2005, 05:42 PM   #7
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They look like roof prisms to me. Did you notice how they were oriented in the binoculars? If you did you would have noticed that they were facing each other. One corrects for the up and down, then, the other oriented at 90 degrees to the first corrects left to right. That's why they put them in binoculars. They flip both ways as long as you use two. Or four in the case of a BI-nocular. As for the application of these to a 35mm adapter, you need to make them twice as big and you loose a bunch of light. Also, if anything gets on any one of those surfaces you will see it.
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Old June 24th, 2005, 07:07 PM   #8
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thats definitely not a dove prism.
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Old June 25th, 2005, 03:18 AM   #9
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i'm no prism expert, but it looks like a roof prism. it's not flat on the top like a dove prism(?). should a roof prism rotate the image 180 deg.? my experience is that when i look thru it, the picture turns out upside down, and not inverted left/right. put if i use on prism to turn it upside down, and one to flip it left/right.. I think they are a bit too small though.
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Old June 25th, 2005, 03:24 AM   #10
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http://www.optics-online.com/rfp.asp
this is the prism, but it doesn't flip right/left! :p wierd.. :D
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Old June 25th, 2005, 05:53 AM   #11
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Quote:
Originally Posted by Rune Hals
i'm no prism expert, but it looks like a roof prism. it's not flat on the top like a dove prism(?). should a roof prism rotate the image 180 deg.? my experience is that when i look thru it, the picture turns out upside down, and not inverted left/right. put if i use on prism to turn it upside down, and one to flip it left/right.. I think they are a bit too small though.

Sorry, I was thinking about my application and left out one part of it. You need a mirror to flip the image up/down and the prism flips it right/left. However, you can find larger roof prisms if you look hard enough and can even get them made to whatever spec you want for a decent price.

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Old June 25th, 2005, 11:19 AM   #12
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Rune,
I assume you have two of these prisms right? You shouldn’t need a mirror if you do. Take them and place them face-to-face (the long flat side). Then slide one up so that it's end is aligned with the others end, (like a periscope). Then rotate one 90 degrees. If you look into one you will see that the other is receiving the image, flipping it then passing onto the one you are looking at which is flipping it horizontally. Maybe a mirror is a better solution, but what you have there (assuming you have another from your binoculars) will do it as well. They are just too small.
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Old July 6th, 2005, 04:00 PM   #13
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thanks for all the replies. i realized that they was too small, but now i know how to use them so i will get some bigger ones. any idea where i can get them?
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