Viewing Lupe

Discussion in 'Talk About Large Format Gear' started by Alan Jones, Sep 30, 2016.

  1. Alan Jones

    Alan Jones New Member

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    Can anyone advise what Viewing Lupe is OK for large format ground glass viewing, Silvestri 45 Degree Tilting Lupe 6x looks OK but can anyone advise of any others or is this OK?
    Regards,
    Alan
     
  2. Alan9940

    Alan9940 Active Member

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    IMO viewing lupes are kind of a personal thing and kind of what you need. The "need" part basically comes down to if you need/want a short or long lupe; I have both, but in prior years when I used a lupe I preferred the long one (Toyo magnifier.) However, for quite awhile now I've just used a pair of magnifying eye glasses because I prefer to have my hands free for working the camera. And, at 5x4 or 10x8 neg size and for the size prints I typically make from these negs focus with the eyeglasses is accurate enough. YMMV, of course.
     
  3. Keith Haithwaite

    Keith Haithwaite Active Member

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    If it can be focused on the ground surface of your viewing glass then it will be fine. Most non-focusing loupes are focused at their foot surface for documents etc and on camera will come into focus on the non-ground glass surface of your screen - 1 to 2mm off where it should be depending on the thickness of you GG. How much that matters I wouldn't like to say.

    However, I'm a bit like Alan in that I use +3 diopter reading glasses (I wear varifocals normally) for composing and focusing but personally, if I need to be really critical, I've always used an old 50mm prime lens in reverse, my current one is a 50 year old Practika lens - and if it gets lost or broken it doesn't cost £100+ to replace.
     
  4. Diz

    Diz Member

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    I use a Nikon Lupe that is also used for looking at 35mm slides and negs. I think it has a x8 magnification. The base is square so it will get into the corners. If only I could fix it to a pair of spec frame I would do so. For the same reason as Alan, both hands free to fight with the wind and dark cloth:p
    Cheers
    Diz
     
  5. Stephen Batey

    Stephen Batey Well-Known Member

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    I use a pair of very strong reading glasses to compose (so that I can get close to the screen) but focus using a now discontinued Rodenstock lupe.

    I'm intrigued by the suggestion that a loup will focus on the "wrong" side of the screen though. If there is a viewable image on both the ground and smooth sides, shouldn't we see a double image?
     
  6. Keith Haithwaite

    Keith Haithwaite Active Member

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    Hmm, I didn't explain this very well did I, let me try again. The point of focus is the image plane - a 'virtual image of sharpness' if you will, but to see this image in the plane where the film will eventually be it needs something partially opaque on which to form but still allow light to pass through so that we can see it - the GG surface. From this it can be seen that an image cannot be formed on the smooth side of the screen because it is transparent.

    However, bear in mind that I said earlier that non-fucusing loupes are normally made to view a flat surface upon which they rest and are pre-focused on this plane. Stand this loupe on the smooth surface of the focusing screen and you will see a slightly oof image. Now move the plane of focus back until it meets the loupe/glass interface (the plane of focus of the loupe) and the loupe will show you the image in focus - but it will be the thickness of the focusing screen away from where it should be.

    Does this make more sense? It's the best I can do without getting into the ray-tracing malarky. I know it sounds a bit odd, having your eye focused on a virtual image, but thats exacly what you do when you focus a telecope or binoculars.

    It's many decades since I did this in class and I suspect that the GG screen we used was very thick in order to emphasise the difference and give substance to the lesson but what the difference will be on a 2mm camera focussing screen to be honest I've never checked, but given the lengths we go to keep film flat it must have an effect visible under close scrutiny.

    I do know that using my reversed camera lens as a loupe I can focus the image anywhere I want but to be absolutely spot-on I keep the GG grid lines in focus while I am focusing the image. I've done it for so many years I do it without thinking now.
     
  7. martin henson

    martin henson Administrator Staff Member

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    My only advice Alan is to buy the best Loupe you can afford, Schneider make very good loupes but are expensive, my opinion they are worth the money and you would not regret buying one, a bad or cheap loupe is a pain in the bottom to use.
     
  8. Ian-Barber

    Ian-Barber Administrator Staff Member

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    I have used Martin's Schneider Loupe and I have to say i was very impressed.

    I own 2 loupes as shown below, the Nikon one is the one I tend to use the most

    s-l1600.jpg

    nikon-loupe-nice-14.99-9541-p.jpg
     
  9. Alan9940

    Alan9940 Active Member

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    Somewhere in Keith's further explanation is probably the reason why my Toyo loupe has a meniscus lens on the gg side of it.
     
  10. Alan Jones

    Alan Jones New Member

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    Thanks for taking the time to comment , decision time now...
     

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