Praktica FX2 prism

[seany65]

I've just bought a Praktica FX2 and I was thinking of getting a 'reversing prism' finder for it, but apparently it magnifies the image by 4x, which I think is more than the focus magnifier of the WLF.

So I was wondering if anyone uses the 'reversing prism' viewfinder with their FX2/FX3?

How does the image it produces compare to the image produce by the WLF, apart form being magnified?

Do we still get to see the full original image-including edges and corners of the frame-produced by the WLF but magnified?

Do we see a section of the image that has been magnified-excluding the edges and corners of the frame-as with the focus magnifier of the WLF?

Any help would be much appreciated.

 

[johnf04]

I have a prism for my FX3, The view is just a little smaller than the view through the WLF - it looks like the view produced by a Zenit. The eye relief is not great, you have to move the camera to see the frame corners clearly. In use, the prism worked fine for me.

 

[seany65]

Thanks for the reply johnf04.

That seems a little confusing to me: "the view is a little smaller", even though according to the manual the finder gives a magnification of 4x, but that magnification would be consistent with not being able to see the whole frame, unless the eyepiece is small which it doesn't look to be.

It seems I'm going to have actually try one before I buy it.

Thanks again.

 

[tunalegs]

4x or .4X? (edit: had to look up the manual, it does say "4 times" but this seems like it must be an error on the part of whoever translated it in the 1950s).

 

[johnf04]

The field of view is smaller - the prism shows around 90% of the viewing screen.

 

[seany65]

tunalegs: Would " .4x " mean the prism's viewfinder image is 1/4 the size of the WLF image?


EDIT: What I actually meant of course, was 'Wouldn't " .4 " mean the prism's viewfinder image is a little under 1/2 the size of the WLF image?"😱


I can't think what number " 4x " or " .4x " could be misprints for.

John:

Do you mean that the mechanism of the prism that is at the bottom and goes adjacent to the focusing screen cuts off 10% of the image if we take the image we can see on the focusing screen using the WLF as 100%?

Do you mean the eyepiece cuts off 10% of the image?

I was wondering if the actual image itself, or rather the objects making up the image are a different size using the prism than they are using the WLF?

 

[tunalegs]

I mean whoever translated the manual into English probably wrote "4 times" when they should have wrote 0.4 times. A Nikon F prism for example has a magnification of 0.6 times (or thereabout). Obviously the prism would not have a magnification of "4 times", but 0.4 times would be believable.


I can't think of a single prism that gives more than 1:1 viewing, even Exakta and Miranda were something like 0.98x magnification - and pretty much everything since has been smaller than that.

 

[seany65]

Thanks for the clarification tunalegs.

 

[seany65]

I looked in a book called "The Praktica Book" by R. Rossing, and it also says

"The reflected image is magnified approximately four times."

I wonder if the author has used the prism?

 

[tunalegs]

It would have to be a mistake, I'd think. This short article gives a bit of explanation of viewfinder magnification: https://photo.stackexchange.com/questions/20597/what-does-viewfinder-magnification-mean


I've never used the FX2 prism, but the FX prism gives an image smaller than 1:1, so I'd assume the FX2 prism to be similar.

 

[seany65]

Thanks tunalegs.

I'd also expect a less than 1:1 view. I think most 'modern' 35mm slrs would give about 0.92x.

It does seem a little unprofessional of KW and the author to get the numbers wrong.

I was a bit disappointed when I got a right-angle finder for my ETRSi that I had, the image was smaller than I'd hoped, and as I had a plain glass focusing screen I found it s bit harder to focus than with the normal hood.

 

[Sumarongi]

I'd also expect a less than 1:1 view. I think most 'modern' 35mm slrs would give about 0.92x.

It does seem a little unprofessional of KW and the author to get the numbers wrong.

No, I wouldn't blame the author.
Very likely, the persons who wrote the manuscript may have written (by hand) *[0,]9* or *[0.]9*, but then the typesetter may have mistaken that as "4".
-- There are even standard works that contain such errors, for many decades again and again quoted as "definitive truth" -- the meanwhile well-known "iron in spinach" myth is such a case 🙂

 

[seany65]

I take your point Sumarongi, there could've been a misprint, but I don't understand how anyone could mistake '0.9' (or whatever it was) for a '4'.

I also think that the Author of the book should've at least used one, even if only for a few seconds, just to see how it works, or at least should've thought " '4X'? That seems a bit much, better check it out."

 

[Sumarongi]

I take your point Sumarongi, there could've been a misprint, but I don't understand how anyone could mistake '0.9' (or whatever it was) for a '4'.

I guess you're British and you write a very pointy "4"?
Many Continental Europeans write it very differently, often nearly like a "Y", thus it can be confused with a sloppy "9", and viceversa of course.

 

[seany65]

I see. Thanks for the info Sumarongi.