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excanonfd
20-Mar-2011, 21:49
Hello,

Does anyone have any experience with one of these viewfinders?

http://cgi.ebay.ca/Right-Angle-Prism-Viewfinder-TOYO-Horseman-4x5-Camera-/270709808207?pt=Film_Cameras&hash=item3f078fdc4f

If this is a pentaprism viewfinder, the image should be right side up, left-right corrected. I am thinking of shooting with 120 roll films only with my 4x5 Technika III, and thought this might be helpful.

Thanks,

Frank Bunnik
20-Mar-2011, 22:59
I use a similar item (but an original one from Cambo) on my Cambo Wide camera. It works fine although it is a little bulky. To use a loupe with it on the Linhof, you have to swing it to the side.

excanonfd
20-Mar-2011, 23:18
Thanks for your reply, does the viewfinder actually have a pentaprism that corrects the image to appear as seen by human eye or is it similar to waist level viewfinder on medium format cameras?

Sevo
21-Mar-2011, 01:26
I am not aware of any prism finder for large format cameras - given the lump of glass needed for it, even an acrylic one would weigh several pounds.

Most reflex finders are of the look-down single mirror type, which gives a upright, left-right-reversed image when looked down into. IIRC at least one maker (Arca?) also offered a frontal view mirror finder (presumably a three-mirror construction) some 25 years ago.

tih
21-Mar-2011, 01:46
It looks pretty much like the (original Linhof) one I have on my Linhof Color, which gives an image that's right side up, but reversed left to right. (Which it obviously must, given that there's a single mirror in the thing.)

It's comfortable enough in use, with a good ground glass and fresnel lens, and swings to one side to let you use a loupe for precise focussing. I like it.

Sevo
21-Mar-2011, 02:03
As I said, there must have been some maker that also offered a Porro type reflex viewer - I positively remember looking through it on a Photokina.

Frank Bunnik
21-Mar-2011, 03:25
There is no prism inside, just a mirror. So the image is no longer upside down but left and right are still reversed.

excanonfd
21-Mar-2011, 18:49
Yes, I thought it would be like a waist level finder on TLRs and some medium format SLRs. I emailed the Seller of the viewfinder about his claim of a prism inside but never did receive a clear answer regarding that.

Thanks,

Emmanuel BIGLER
22-Mar-2011, 04:38
Hello from France !
Reflex viewfinders are as old as Photography itself.
A reflex mirror was already in use in early daguerreotype cameras ! (http://leonardjoel.com.au/images/lots/127425_1_popup.jpg)
For the dag' , a mirror not only displayed the image with the 'up' upside, but also displayed the image as actually seen on the dag' i.e. left-right reversed.

Edmund optics (http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productid=2077&StartRow=41&PageNum=3) has a choice of first surface mirrors if you want to fabricate your own reflex viewer. You need a first surface optical mirror of quality so-called '4-6 wave first surface mirror'.
Examples of prices :
for a mirror of area 4"x5", thickness 1/4" = $35
area 5x7", thickness 1/16" = $45.5

Then you'll optionlly need a positive lens element or a low-power loupe, or a pair thereof for a binocular viewer. A good starting point for the required magnification are 2x loupes (this corresponds to a focal length of 125 mm, about 5") and you just have to make a kind of D-I-Y box to combine both elements. A 4x loupe is definitely too short in terms of focal lengths (4x = focal lenghts 62.5 mm, i.e. about 2"-1/2) to allow sufficient clearance for the mirror, and will never cover the whole 4"x5" image field.
You can get inspiration for a folding reflex viowfinder here (sorry, the text is in French, but the pictures are self-explanatory. (http://www.galerie-photo.com/construire-viseur-chambre-arca.html) The author, Hervé Elllena, has built this viewfinder for his own camera model, but you can adapt to any kind of view camera. :)