New homemade DOF adapter scheme at DVinfo.net

Plamen Petrov · May 25th, 2007, 04:34 PM

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!

Cole McDonald · May 25th, 2007, 07:34 PM

Looks very nice, simple...where does one go about getting a pentaprism? Outside should look like a tube with a bend in it.

Alex Chong · May 25th, 2007, 10:07 PM

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.

Plamen Petrov · May 26th, 2007, 04:45 AM

Quote:

Originally Posted by Alex Chong

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.

Yav Bonev · June 2nd, 2007, 09:25 AM

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!

Paul Cascio · June 2nd, 2007, 12:13 PM

So why hasn't someone used a pentaprism from a 35mm SLR camera? I'm assuming ther's a good reason.

Plamen Petrov · June 2nd, 2007, 02:21 PM

Quote:

Originally Posted by Paul Cascio

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? :)

Bob Hart · June 2nd, 2007, 02:39 PM

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.

May 25th, 2007, 04:34 PM	#1
Plamen Petrov Regular Crew Join Date: Feb 2005 Location: Sofia Bulgaria Posts: 147	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! Attached Thumbnails

May 25th, 2007, 07:34 PM	#2
Cole McDonald Trustee Join Date: Nov 2005 Location: Sauk Rapids, MN, USA Posts: 1,675	Looks very nice, simple...where does one go about getting a pentaprism? Outside should look like a tube with a bend in it. __________________ Web Youtube Facebook

June 2nd, 2007, 12:13 PM	#6
Paul Cascio Trustee Join Date: Sep 2004 Location: Bristol, CT (Home of EPSN) Posts: 1,192	So why hasn't someone used a pentaprism from a 35mm SLR camera? I'm assuming ther's a good reason. __________________ Paul Cascio www.pictureframingschool.com

May 25th, 2007, 10:07 PM	#3
Alex Chong Regular Crew Join Date: Jun 2004 Location: Brunei Posts: 140	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.

June 2nd, 2007, 09:25 AM	#5
Yav Bonev Tourist Join Date: Mar 2007 Location: Sofia, Bulgaria Posts: 1	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!

June 2nd, 2007, 02:39 PM	#8
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	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.