question about view cameras and focusing

Discussion in 'Large Format Cameras and Accessories' started by BetterSense, Jun 18, 2009.

  1. BetterSense

    BetterSense Member

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    I don't know anything about view cameras and have never even seen one used. I understand that you can look at the back of the camera and see the image upside-down on the ground glass, and then you use that to focus the camera.

    So that means the lens is focused on the ground-glass surface. So how, when you put in a film holder and retract the darkslide, is the lens focused on the film then? It would seem that due to the thickness of the film holder, it would be in front of the ground glass surface. Do you remove the ground glass before inserting the film holder?
     
  2. Jim Noel

    Jim Noel Member

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    The distance from the lens to the ground glass is exactly the same as the distance from the lens to the film once the holder is inserted.
     
  3. dpurdy

    dpurdy Member

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    The ground glass is held generally by spring steel that allows it to open up for the film and put the film in exactly the place the glass was.
     
  4. Bruce Watson

    Bruce Watson Member

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    To be fully correct, the image is upside down and backwards. There's no reason to fear this, though many newbies do. It's actually a great composition tool. And after you've worked with a view camera for awhile your brain will adapt and you'll only see the image upside down and backwards if you will it.

    Design of view cameras is such that the ground glass is in a frame that's held in place by springs. This frame is pulled backwards (away from the lens) and the film holder is inserted in front of the ground glass. If the camera is set up correctly (and it's fairly rare to have a problem with this) registration between ground glass and film is excellent. So what you see on the ground glass is what you get on the film.
     
  5. dpurdy

    dpurdy Member

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    To be absolutely absolutely correct, the image is upside down but not backwards. It just reads the other direction from being upside down. It is not like a Rolleiflex ground glass that shows the image backwards (though right side up).
    Dennis
     
  6. John Koehrer

    John Koehrer Subscriber

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    If you like to fiddle about try using a piece of ground glass or frosted plastic on your 35. Just press it against the film rails of your camera & open the shutter on B it's the same thing but smaller.
     
  7. BetterSense

    BetterSense Member

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    I've done that before to set the focus on non-SLR cameras. I focused the viewing lens and then put a piece of ground glass on the back and adjusted the taking lens so that the image on the ground glass was in focus.

    It surprised me to see that the image on the ground glass was color.
     
  8. David Brown

    David Brown Subscriber

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  9. David William White

    David William White Member

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    hehehe. Once in a while when I'm shooting someone with the 4x5 -- and they know I shoot in B&W -- we switch positions and I let them see me under the darkcloth on the ground glass. Comments I've gotten: "Oh, it's digital!", or "Hey, this is in colour. You said it was black and white!", "Why is the camera upside down?", to which I sometimes tell them that they have to stand on their head.
     
  10. Sirius Glass

    Sirius Glass Subscriber

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    "Oh, you must have the lens on upside down!"

    Steve
     
    Last edited by a moderator: Jun 18, 2009
  11. Bruce Watson

    Bruce Watson Member

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    Wrong. The image on the ground glass is upside down and backwards. It's the laws of physics. Look up how a lens projects an image.
     
  12. Paul Cocklin

    Paul Cocklin Member

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    Bruce, not that it's any of my business, but I think you're flipping the image and then reversing it, and dpurdy is rotating the image. In both cases, left is right and up is down. What a crazy world we live in. :smile:
     
  13. dpurdy

    dpurdy Member

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    If you stand on your head and look at the image it isn't reversed. It isn't backwards. However it does feel backwards just to look at the image. Because things pointing "left" in right side up orientation will be pointing "right" when upside down. Actually it might be easier if the image was both upside down and backwards because in standing there composing the upside down image I quite often reverse it in my mind as if I could lift the image from the bottom straight up to the top. But it must be rotated.

    The reason an image in a WLF is right side up and backwards is because it is bounced off a mirror. You could do the same thing with your view camera. Hold a mirror under the image angled so that you can see it, it will be right side up and backwards.

    If the image on a ground glass were actually upside down and backwards, you could hold a mirror under the ground glass angled for you to see and it would be right side up and oriented correctly.
     
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  15. Paul Cocklin

    Paul Cocklin Member

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    Incorrect. The mirror would not reverse side to side, it would only reverse up and down.
     
  16. Bruce Watson

    Bruce Watson Member

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    I'm not flipping anything. The lens projects an image that is both upside down and backwards. This is just simple physics. All lens systems do this, from the human eye to cameras.

    The reason DSLR camera use a pentaprism is that to "correct" the image in the viewfinder they have to flip it twice -- once vertically, then again horizontally.
     
  17. dpurdy

    dpurdy Member

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    Well this is all good fun right? Perhaps just a different way of thinking of the same thing. But if you aim your view camera at a word that of course reads left to right, when it gets projected onto your ground glass it is upside down. If you stand on a chair and turn your head upside down, the word will still read correctly. It won't look like a mirror image because it is only upside down and not both upside down and reversed. IF you hold a mirror under the ground glass while you stand behind the camera and angle the mirror up so you can see the image as if it is right side up, it will be reversed and the word will read backwards.

    This is all humorous and a bit difficult to explain, but I am sitting 10 feet from an 8x10 camera on a still life set and there is no question that what I am saying is correct. My flowers which point to the left in reality are upside down and thus pointing right in the camera. If they were both upside down and reversed they would point to the left in reality and still point to the left when upside down.

    I think we are just stating the same thing differently
    Dennis
     
  18. Bruce Watson

    Bruce Watson Member

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    Nope. You'd have to flip it twice. Once vertically, once horizontally. Which is why there are pentaprisms in DSLRs. They have to flip it twice because the image is both upside down and backwards.

    This is clearly beyond my ability to explain to you. Such is life; I'm not a teacher. Find someone near who uses a view camera and they can give you a demonstration maybe. Or a local physics teacher can show you maybe.

    BTW, if you are standing on your head looking at the ground glass, it's you who have flipped twice. Once horizontally (which puts you on your head looking away from the ground glass) and once vertically (flips you 180 degrees so you are looking at the ground glass).
     
  19. dpurdy

    dpurdy Member

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    What if I just do a cartwheel and stand on my hands. I am only rotated and not flopped. Just once.
    Dennis
     
  20. bobwysiwyg

    bobwysiwyg Subscriber

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    If I could do cartwheels, I wouldn't care what the image looked like. :smile:
     
  21. cowanw

    cowanw Member

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    I will attest that the Cambo reflex mirror will end up with a right side up but backwards image.
     
  22. Ian Grant

    Ian Grant Subscriber

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    Bruce, Dennis is right, yes the image is Upside down & Reversed left to Right on the screen, but turn it 180 degrees and it's correct. Just try holding a negative with the emulsion side away from you, image upside down, thats the same as a focus screen, now revolve it the 180 degrees and everything is correct.

    Add a mirror and you only correct the one dimension hence left & right are switched (backards image).

    Ian
     
  23. Paul Cocklin

    Paul Cocklin Member

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    Visual Aids

    The real problem here is the misunderstanding of the vernacular. Upside down does not mean turning your head 180 degrees so your skull is pointing at the ground. You're changing your perspective when you do that, which is not what the camera lens is doing. Bruce is correct in that the lens (all lenses) reverse the image in both vertical and horizontal planes.

    I'm actually bored enough today to have spent 4 minutes putting together visual aids.

    First image is a flower in a vase, as we would see it with just our eyes.

    Second image is what would be considered upside down. Notice that there is no side to side reversal.

    Third image is what would appear on the ground glass of a view camera.
     

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  24. dpurdy

    dpurdy Member

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    Good drawings. Yes as I said we are just saying the same thing differently. To me the second picture is not just upside down it is flopped. It is upside down and backwards. The 3rd image is merely upside down. If you actually take a piece of paper and make that drawing in picture #1 and then spin it round till it is upside down you get picture #3. If you spin it round upside down and turn it over you get picture #2. That is if you can see through the paper.

    Dennis
     
  25. Paul Cocklin

    Paul Cocklin Member

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    Yes, but Dennis, I think you're thinking of it as a function of perspective. If you are looking at something and you turn your head upside down (you know what I mean) then you are correct. But that's not what a lens does. The lens does not rotate the image, it passes light through so that light that strikes on the left exits on the right, and top/bottom.

    As I said, a problem of semantics and perspective. Thanks for the compliment of the drawing. I think I should give up photography and become a painter. :D
     
  26. Sirius Glass

    Sirius Glass Subscriber

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    Finally, cleared up with drawings. I did not jump in on this because I have found that sometimes to work out problems it is best to maintain a good watch to work ratio!

    Steve