Can anyone share schematics / specs for a medium format reflex viewer ?

Does anyone have the schematics / specs / drawings for a medium format reflex viewer ?

I would like to build a custom reflex viewer to use with my spare Mamiya 7 body, for composition purposes. I have attached an NPC polaroid back to the camera body, but removed the back processing piece, which allows me to view the image projected on the fiber optic glass.

I am attaching a photograph of the fiber optic glass with the projected image on it. I need to deflect the image, at least top to bottom.

In detail, I would like to know what the size, shape and angle of the mirror need to be, as well as it's distance, in relation to screen on which surface stands the projected image to be reflected.

Thank you to all the readers and tech experts sharing their photographic knowledge!

Not that certain what you are trying to achieve, but maybe something like the reflex finder for a Horseman VH?
https://www.ebay.com/itm/Horseman-A...820579?hash=item2391bb3563:g:d1UAAOSwH1NZgr98
I don't have schematics, never seen one in real life. It might be a starting point. Maybe even an end point- get one, modify the opening, and attach it to your Polaroid back>

Dan Daniel said:

Not that certain what you are trying to achieve, but maybe something like the reflex finder for a Horseman VH?
https://www.ebay.com/itm/Horseman-A...820579?hash=item2391bb3563:g:d1UAAOSwH1NZgr98
I don't have schematics, never seen one in real life. It might be a starting point. Maybe even an end point- get one, modify the opening, and attach it to your Polaroid back>

Click to expand...

Thank you Daniel ! I already knew about the existence of the Horseman, which I have been tempted to get for a while. I have never been able to find one in Europe, however, and with shipment costs and vat plus import duties it will be over 300$, which I consider to be a lot for a viewing accessory.

Also, I prefer to have a WLF type of viewer, being used to the Hasselblad and the Mamiya RZ.

Thanks for the kind reference anyway !

Pietro

all you need is a mirror at an angle so you can look down at 90deg and see the full frame. that will turn the image upright.

another solution would be to find a surplus prism you can custom hinge to your frame.

Giovanna said:

In detail, I would like to know what the size, shape and angle of the mirror need to be, as well as it's distance, in relation to screen on which surface stands the projected image to be reflected.

Click to expand...

I guess it even works without knowledge.
Just hold a plain mirror at an angle that suits you angled at the lower edge of the screen back and mark on that mirror the outer limits of the image of your screen. That would be the minimum trapezoid dimension of your final mirror.

If you chose an angle of 45° the image om the mirror woud not even be trapezoid and you could cut a rectangular mirror.

Set a first surface mirror at a 45 degree angle to the film plane. It should reflect the image area of the taking lens/format.

You can probably adapt a Cambo T-20 or T-21 viewer cheaper than the horseman, though it might be a tiny bit bigger.

You will really need a ground glass, and probably a fresnel, to make this useful. The fiber optic plate is a bit of a red herring here - you don't really need it, and it's a hindrance in a way. you want a ground glass and/or fresnel at the focus plane. Then put the mirror to reflect that. Get the fiber optic plate out of the mix if you can, it lowers resolution and it's only purpose is to extend the image back to the plane of the polaroid film. It's a bit of a hack solution, even for that purpose.

And how do you plan to keep the lens open for viewing? Normally that's not easily done short of taking a bulb exposure and opening the back, but even that might not work well, if at all.

With the 'light pipe' in place, you will still be viewing an aerial image. Is that what you want?
Usually the light form the taking lens focuses on a semi-transparent material (ground glass, etc).

I know it's a bit of a stretch, but I think it's going to work. The fiber optic plate actually transmits light evenly and extremely well - actually much better than the ground glass + fresnel combination on my Horseman 45HD. It is so beautiful already seeing the image as it is. I can clearly see the focus shifting and the depth of field changing, don't have any dark corners and don't even need a dark cloth (unless I have direct sun light on me from behind).
In terms of how to keep the shutter open, you need to set the Mamiya to multiple exposure and on bulb, and just keep the shutter release button pressed.
Again, most of the times I use the Mamiya 7 hand held, but at times I need to do a precise composition, on horizontal images, and this second body with a custom made viewer could really come in handy.
I think I am going to try and make a design and 3d print a super light weight prototype that can fit a mirror inside at a 45 degree angle, and a viewing screen on top (just like other medium format WLFs)!