DIY idea for 35 mm adapter

[robertwerden]

The new wave of 35 mm adapters use a flip unit to right the image in your view finder. The method of doing this is by using a Porro Prism. Porro prisms are found in binoculars of the old days. Todays newer binoculars use Roof prisms, which eliminate the need for a 90 degree zig zag in line of sight.
So would it not be a better idea to hack into a monocular that uses a roof prism and simply remove the prime lens from the monocular as well as replace the small achromat with a larger one?

Here are some photos to better show my thought process here.
As you can see the Roof prism side (left) shows the lenses in the same order as a 35 mm adapter.
In order going from top of image to bottom
1. Eyepiece lense. (remove because your camera lens would replace it)
2. Achromat (remove and replace with one that is the same size as you would normally get with a 35 mm adapter such as 72mm)
3. Roof Prism (performs the image flip)
4. The focusing screen would replace the next lens.
5. Your Nikon or other Prime lens would replace the objective lens.

Tell me what you think of this type of set up.

 

[thekreative]

I think the key works are "more lossy"

http://en.wikipedia.org/wiki/Schmidt-Pechan_prism

 

[robertwerden]

Interesting since they bounce light just about the same (5 vs 6 times)
Also something to consider is the surface area can be larger in the same about of space inside the tube. So the size of the reflected image may compensate for the loss of light due to light bounce.

 

[thekreative]

I think the problems are the angles of reflection. Special coatings are required to increase the reflective qualities of the angles. Also the light leaving one prism through air and into another is a weak point. That said, if its made right its a way better design for an adapter.
Now to start building one.......

 

[MatzeB]

I think it could be difficult to find a schmidt pechan prism
that's big enough. You need a free aperture of at least 40mm, or?
(I don't have a flip unit).

 

[robertwerden]

I dont know how big the prism is in the commercially available flip units.
Does any one have a measurement?

 

[ReneH]

The only way to begin to even know is to try making one, at least from there you can figure out where to start.

 

[robertwerden]

Ya I plan on it.
Ill let you know what I get as far as results.