viewfinder magnification

Discussion in '35mm Cameras and Accessories' started by msbarnes, Oct 20, 2011.

  1. msbarnes

    msbarnes Member

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    why don't many cameras have 1:1 viewfinder magnification? Is it difficult to achieve? This is on both RF's and SLR's. What gives?
     
  2. polka

    polka Member

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    Anyway, for the SLRs, the viewer magnification depends on the focal of the lens attached : with wide-angles the image seems smaller, with the teleobjectives they are larger. With my Topcon, the magnification is 1:1 for my standard 58mm lens. It is also the case of my Spotmatic with the Zenit Helios44 (which focal is also 58mm).

    Maybe the magnification is a little less than 1:1 on SLRs with 50mm lenses, because otherwise the viewing angle of the viewfinder would be to wide for comfortable viewing ?

    Paul
     
  3. Markster

    Markster Member

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    The viewfinder has to be smaller by definition. It has to have a moving mirror. That means its dimensions fit inside the normal "view" dimensions inside the mirror chamber...

    It's just one of the issues with splitting a view off in a separate direction (the viewfinder) from where it needs to go naturally (the film plane).
     
  4. ic-racer

    ic-racer Member

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    Back in the day when you had to actually focus an SLR yourself, the focusing screen image was quite large and wide and frequently gave a 1:1 image when a 50mm lens was on the camera. I notice that post 1980s autofocus cameras, like Nikon f100 and n75 have what I call 'tiny' focus screens. I presume because the camera will focus for you and you don't need to see the image 'close up.' In fact the n75 gives a 1:1 view only with an 85mm lens. So I wouldn't even try to use that camera (or the F100) with manual focus lenses.
     
  5. Markster

    Markster Member

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    Forum ate my post! Gah!

    Second try: Even ones in the 80s never had 1:1 zoom. They have at best 0.97x zoom or something close. The only way to get full 1:1 zoom would be to have no viewfinder at all -- like one of those glass plate cameras from the 1800s. Otherwise, any diversion of the light stream is going to cost some small margin of viewing area just because of the framework of the mirrors and the reflexive prisms in the viewfinder.
     
  6. Ralph Javins

    Ralph Javins Member

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    I think Paul is right.


    Good morning;

    As Paul has said, with most of the SLR cameras where you still could do some of the work yourself (other than just aiming it and pressing the shutter release button), the lens focal length that seems to produce a true 1:1 viewing image with true perspective as you see with your eye, seems to be right at about 58mm. Many of the major SLR camera manufacturers back in the early and middle 1960s made available a 58mm lens as one of their premium and professional offerings. There must be some reason why they departed from the "normal" 35mm film focal length for a "standard" lens of only 50mm.

    And, I can add both Nikon and Minolta to the list of manufacturers Paul provided. Minolta was still offering a 58mm focal length lens at least into the late 1970s.
     
  7. Bob-D659

    Bob-D659 Member

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    58mm lenses, ie, the Nikon 5.8cm f1.4 were not retrofocus lenses.
     
  8. Markster

    Markster Member

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    I thought he was talking about usable area in the viewfinder vs what shows up on film?


    Color me confused then.
     
  9. AgX

    AgX Member

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    Markster, these are two issues: the finder image magnification, and the ratio (given as percentage) between finder image area and film gate area.
    The latter often differs due come up for the reduced size of image area in a framed slide. Furthermore is gives some reseve in case of misalignement between finder and film gate.
     
  10. lxdude

    lxdude Member

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    Your assertion that no viewfinder showed 100% of the final image is incorrect. The Nikon F, F2, F3, etc. show 100%.
     
  11. John Koehrer

    John Koehrer Subscriber

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    1:1 magnification, not % displayed in finder.
    So ~58mm lens = ~1:1 image size in finder.
     
  12. polyglot

    polyglot Member

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    In an SLR, the apparent magnification depends on the lenses between the prism and your eyes (viewfinder magnification) as well as the objective lens' focal length; for a given viewfinder magnification, you will obtain a 1:1 view at some objective particular focal length. You can get a magnifying eyecup that clips over the back of the prism and gives you (typically 1.4x) greater magnification - I have the Pentax version installed on my Sony DSLR that makes manual focusing a little easier though of course at the cost of a dimmer image.

    There are plenty of SLRs with 100% viewfinder coverage; it's just that they're a bit annoying to build because it requires an oversize mirror; there is nothing special about the mirror that means you need to have a reduced view. A bunch of Nikon Fs, as well as Minolta 9 and Sony A900.
     
  13. wiltw

    wiltw Subscriber

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    Gosh folks are mixing up issues! There are two characteristics about viewfinder size:
    1. amount of area of the frame of the camera a.k.a. 'viewfinder area', such as 97%
    2. magnification presentation thru the eyepiece, e.g. 0.92x.

    The Olympus OM-1 showed 97% of the frame, the Nikon F and F4 showed 100%.
    The Olympus OM-1 showed the viewfinder at 0.92x magnification (with 50mm lens), the OM-4 showed 0.84x magnification, and the Nikon F4 showed 0.7x magnification.

    The reason for the shrinkage in viewfinder magnification (even while showing 100% of the frame area) was the need to cram in all of the camera status displays in the viewfinder area surrounding the focusing screen area!
    If manufacturers tried to retain the magnification factor, the pentaprism housing would have grown larger in size to accommodate the larger pentaprism needed to view the 24x36mm focusing screen and the area surrounding it which housed the status displays, increasing cost and price and bulk and weight of the camera.
     
    Last edited by a moderator: Oct 23, 2011
  14. Ronald Moravec

    Ronald Moravec Member

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    Simple cost, size, and weight reduction. 75% + of the people can`t see the difference anyway. When they want to get real cheap, they use mirrors instead of a prism.

    If you look at my D3 & D700, the D3 has 1:1 and it has an obviously larger pentaprism to accomodate. Same with my F2 ( 1:1) and FE2.

    Katz eye can not make a focus screen for the D3 because it is slightly larger than than the D700 which is the size limit blank they can make. The D3 and D700 are both full frame digi cameras for those who do not know.