Reflex viewfinder for whole plate Chamonix

[Greg]

Have, use and love my 4x5 Sinar Norma with Sinar's binocular reflex back and my Charmoix (in the field) with its Charmonix reflex back.

My most used camera is a whole plate Chamonix. Have obtained an 8x10 fresnel lens for it that I have to cut down and adapt to the back. Now really want to have a reflex viewer to use with the camera. VIEWCAMERA magazine once had a single page article on someone who had a relax viewer fabricated for his 11x14 view... a custom one on one fabrication.

What direction to pursue? Anyone out there have any suggestions?

thanks
Greg

[LabRat]

Ambitious project, but let me take a stab at it...

The first thing is to view the back image through the fresnel and note how far your viewing distance is when you are viewing directly on the center axis, that you can see the entire image evenly lit corner to corner... Note that... Then go to the dollar store and get one of those cheap magnification glasses (or reading glasses lens, or other low power + lens) with a FL about your viewing distance you found above... Repeat the on-axis test above with the lens, and check the coverage to the corners, and see if that will do 'ya about right...

The next hurdle is the housing... If you made something out of rigid wood or metal, you would quickly tire of having to lug around this big "box" on location (but maybe OK in the studio), and it's weight would strain the back + it's mountings (and the back would have to be drilled/modified with brackets to hold it, etc... Bad for re-sale!!!)... My suggestion would be if one could make it out of a lightweight material such as black mattboard, gatorboard, corrugated poly plastic, etc, that it might not be so heavy that it could be attached to the back with velcro strips, if lightweight...

The hot concept would be to take the above materials and make tab flaps on the seams of the "box" (that could be covered with velcro) so it could fold into the shape of the "box", and then undone to carry it flat... I strongly suggest using a thin plexiglass mirror (even with a little ghost image) or metal mirror, rather than using a FS glass mirror that will break...

Now one thing would be that you might have to choose if this will be used for H or V orientation if it is a reflex finder... If it was like a long "dunce cap" straight shape, either would be easy, but dedicated for reflex viewing, you will probably have to choose... Also remember this camera is bigger than your 4X5, so when viewing from above, the camera will have to be lower, so a little like shooting from waist level...

You might be able to mock this up with cardboard or posterboard to see if it might work, then try the stronger light materials after you made a cutting guide...

My thoughts...

Good Luck!!!

Steve K

[mdarnton]

I've done some thinking about this for a while, too. How about this:

-Start with a 4-sided light metal or wood frame against the back.
-Hinge a (mounted?) mirror to the bottom of the frame with book tape (film holder flap tape)
-Built collapsible cloth panels for the sides, attached to the frame and mirror sides to allow
the mirror panel to fall outwards to 45 degrees. More book tape
--For the top, another flat panel hinged with tape to the frame to fold over the collapsed
mirror and sides as a cover, supported by them when they are unfolded. Has edge flaps
that overhang the outside, for light traps
--Appropriate magnifier in the top panel

The whole thing could be square, able to be taken off and reattached as the back rotates. The
obvious means for this would be magnets.
It would be compact and relatively light.

The one problem I see is that I'm not so sure I could focus well from the established distance.

There was a thread a while ago about an Italian fashion photog who has a reflex viewer for
the back of his 8x10 camera, visible in a video clip about him, but I don't remember his
name.....

Ah, here it is: http://www.largeformatphotography.info/forum/showthread.php?112382-anybody-recognize-this-viewfinder-on-the-8x10-deardorff&highlight=8x10+reflex+finder

Here's a really nice rundown on reflex finders, including the 8x10 Toyo mentioned in the other
thread: http://www.bnphoto.org/bnphoto/LFN/ReflexFinders1.html
My idea above is somewhat similar to the Wista finder illustrated way down the page.