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Old May 25th, 2007, 05:34 PM   #1
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New homemade DOF adapter scheme

Hi,
Im making my DOF adapter by myself, with static GG, and with absolutely unknowledge of photography and lenses I got a pretty good results with my home made adapter (actually I am a professional musician, hehe). But I am not satisfied yet, because my final target is to make it so that the picture is not flipped. I am totally against any additional monitor or turning the cam upside-down. So, I am on way to finish my flip enhanced adapter soon. I will use a mirror and pentaprism so that to solve any uncomfortable decisions. My version of making 35mm DOF adapter is much easier than it looks on the scheme here. The proportions are not exactly as shown on the diagram, but the base of the idea is clear, I think. Attaching and stabling of all the elements is easy after a strict positions prepared. The only thing I need to think is the shape of the outer body of the construction. So, share your mind and advises about that matter.
Stay tuned, I will be back soon!
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Old May 25th, 2007, 08:34 PM   #2
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Looks very nice, simple...where does one go about getting a pentaprism? Outside should look like a tube with a bend in it.
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Old May 25th, 2007, 11:07 PM   #3
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If that prism isn't a roof prism, then you will still get the image left to right and vice versa although the image is upright. You need a roof prism to get the image upright. Mirror setup will be the best. Cheap and effective. The only thing to watch out for is dust collecting on the mirror and spoils the video.
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Old May 26th, 2007, 05:45 AM   #4
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Originally Posted by Alex Chong View Post
If that prism isn't a roof prism, then you will still get the image left to right and vice versa although the image is upright. You need a roof prism to get the image upright. Mirror setup will be the best. Cheap and effective. The only thing to watch out for is dust collecting on the mirror and spoils the video.
I don't know if the name of the prism is "roof" or not, it is just a pentaprism from any analog photocamera. I use it from russian "Zenith", but it is the same in the other cameras, I think.
The most I want is to avoid any bending of the tube or just a little bit only.
Also, the best choice is to attach the prism directly on the focusing screen.
Also, I found out a very appropriate prism without any bending, called "Abbe-koenig-prism", u can see it below. It is more than enough to be placed in a tube with size equal to the lenses and the objective. So, if all of you can find such a prism, please let me know how to get it too.
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Last edited by Plamen Petrov; May 26th, 2007 at 07:27 AM.
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Old June 2nd, 2007, 10:25 AM   #5
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If you can achieve the same results as the other adapters, but with the advantage of a non-flipped screen, then in my books, you're nothing less of a revolutionary :) What kind of mechanism will you be using for the vibration of the ground glass? Also, do you think any additional light loss will occur, due to the additional elements, such as the prism and the mirror?

Uspeh, pich!
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Old June 2nd, 2007, 01:13 PM   #6
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So why hasn't someone used a pentaprism from a 35mm SLR camera? I'm assuming ther's a good reason.
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Old June 2nd, 2007, 03:21 PM   #7
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So why hasn't someone used a pentaprism from a 35mm SLR camera? I'm assuming ther's a good reason.
Yeah, I am gonna use exactly such a pentaprism, same in my scheme above.
About the light loss: I am not worried about that because almost ALL the standard movies show EXACTLY a light so similar to the result in my idea. Also, the most of the cams shoot brighter than a movie, so I think that loss is for good.
About the vibrating of GG: I will avoid it!!! When you find a much better way to get pretty cool result with static GG, of course you would forget about any vibrating, right? :)
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Old June 2nd, 2007, 03:39 PM   #8
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If you go back far enough in the threads, you will find there are some ideas that led to dead-ends.

The SLR camera pentaprism image path was too narrow for most prosumer video cameras if I recall correctly though I think it was suggested as usable for small palmcorder style cams.

The movietube design uses a prism (Schmidt???) cannot remember now and is a static solution with large area wax GG in a condenser sandwich which apparently works quite well and I understand, maybe incorrectly is a benchmark for static designs.
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