Lens equivalancy to 35mm

Discussion in 'Large Format Cameras and Accessories' started by EASmithV, Jan 15, 2009.

  1. EASmithV

    EASmithV Member

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    I heard a while ago that if you take the lens and divide by 3, you get the 35mm equivalent. I have used this as my rule of thumb for quite some time. However, I was just looking at the 300mm lens I currently have mounted on my 8x10, and IMHO it doesn't look like a 100mm zoom on a 35mm ...
     
  2. tiberiustibz

    tiberiustibz Member

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    I believe the ratio is more like 8.
     
  3. Ole

    Ole Moderator Staff Member Moderator

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    First of all, the factor of 3 is used for 4x5" to 35mm, NOT for 8x10" to 3500m. Double it for 8x10".

    Second, the aspect ratio is different enough that the "equivalency" is of limited useability.

    Third, at moderate distances the bellows extension needed to focus a LF camera (beyond infinity focus) throws the whole "equivalence" off.

    A 300mm lens on 8x10", focussed at infinity, has a focal length slightly shorter than the film diagonal. So would a 40mm lens on a 35mm camera.
     
  4. Pinholemaster

    Pinholemaster Member

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    The secret is to forget about 35 mm equivalence. Learn to see the world via the lenses for your 8x10. With practice it will become intuitive.
     
  5. BradS

    BradS Subscriber

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    Exactly what Walter said.
     
  6. wiltw

    wiltw Subscriber

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    Measure the height of the frame in millimeters. Now use that number as the divisor, and the lens FL as the dividend...e.g. 150mm lens on 4x5 is 150 / 90 = 1.66, so this would be equivalent on 135 format to 24 * 1.66 = 40mm FL

    This technique is what Sinar uses.
     
  7. mhanc

    mhanc Member

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  8. Martin Aislabie

    Martin Aislabie Subscriber

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    As ever – nothing is straight forward in LF

    There is no good hard lens equivalence between 35mm & LF

    The aspect ration of 35mm is 3:2, with LF its 5:4

    Get the vertical equivalence right and the horizontal is off & visa versa

    There are several ways to do it:-

    Guess - it’s somewhere between 3 & 3.6 at infinity compared to 5x4 (double that for 10x8) but the ratio goes out of the window as you rack out the bellows.

    Experiment - find a friend who has a bunch of lenses and try them out for size to find some that suit you

    Scale up or down from a Lens you already own in that format (the ratio of 1.5 to 2:1 seems a reasonable spread in LF – you can then go back and fill in the gaps as your needs require)

    Good luck

    Martin
     
  9. Ian Grant

    Ian Grant Subscriber

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    Just use the rough rule of thumb Ole & others mention 3x for 5x4 & 6x for 10x8 formats.

    As Brad & Walter say it's not really that relevant it's how you see with that format.

    Ian
     
  10. mjs

    mjs Member

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    Get yourself a piece of dark colored cardboard and cut a 4" x 5" hole in the center. Glue a piece of string, 12" or more long, to the bottom center of the card. In other words, make yourself a viewing card. For 4x5, the distance from your dominant eye (measured from your cheek is close enough,) to the cardboard is the focal length of the lens which would reproduce the view. Double the measurement for the equivalent 8x10 lens. Now you can walk around and expose "air film" all day, and in the process learn what focal length lenses your vision gravitates toward.

    Mike
     
  11. Maris

    Maris Member

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    It is possible to calculate geometric equivalents between 35mm and LF lenses but the numbers may not end up being a good guide in transferring one's "vision" between formats.

    More than thirty years ago I shot 35mm with wide and wider lenses. I had one of the first Spiratone 18mm lenses on my Pentax and knew for sure that I would need an ultra-wide lens for my new Nagaoka 8x10. All I could afford at the time was a Fujinon W 300 f5.6 so the LF wide never got purchased. And I ended up not missing it. Why?

    I realised that I was using the Spiratone 18mm lens for DEEP landscapes, connecting foreground and background and keeping everything sharp. The WIDE aspect was a side effect that, often as not, condemned the pictures to being 85% periphery and only 15% middle.

    The 300mm normal lens on the 8x10, combined with the powers of the Scheimpflug condition, delivered that DEEP all-in-focus landscape without battling with the challenging "emptiness" that often infects the ultra-wide view. It would have been a mistake for me just believe the numbers and translate my 18mm Spiratone lens into a 115mm Grandagon!
     
  12. Steve Hamley

    Steve Hamley Member

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    Oh, let's really complicate things and point out that as you progress in photography, your vision may change. I started out with the standard 150-210-300 set in 4x5 and ended up selling them all and going to 135-180-270. I'd suggest a "normal" focal length like 150mm or 135mm and see how it feels before acquiring other lenses.

    That's because if your subject matter is open landscapes like in the West, a longer 180mm-210mm may be "normal" while the more constricted landscapes like I have in the East may call for a shorter 135mm. If I average 135mm and 210mm, I get 345mm/2 = very close to 150mm, which may or may not suit you.

    Cheers,

    Steve
     
  13. 2F/2F

    2F/2F Member

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    Since the two formats have different aspect ratios, there are no *direct* AOV equivalents. You get near-direct equivalents with 6x9 format, but not 4x5, or most others.

    When most people speak of equivalents, they are speaking of diagonal AOV equivalents. These give you a good general idea, but will leave you disappointed if you need an exact equivalent for some reason.

    I prefer to look at horizontal and vertical AOVs. Each one of these has a different factor to find an equivalent. The factor for horizontals is approximately 3.6. The factor for verticals is something that I forgot, and the online AOV calculator I like is not working right now.

    With a horizontal AOV equivalent, the horizontal AOV will be the same as the 35mm equivalent, but the vertical AOV will be wider than the 35mm lens.

    With a vertical AOV equivalent, the vertical AOV will be the same as the 35mm equivalent, but the horizontal AOV will be narrower than the 35mm lens.

    Depth of field will always be greater for a given AOV with a smaller format film, since longer focal lengths are needed to achieve the same AOV.
     
    Last edited by a moderator: Jan 20, 2009
  14. Ian Grant

    Ian Grant Subscriber

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    In reality I tend to think of both dimensions as I'm regularly shooting with 5x4 usually with a 135mm or 90mm lens plus a 6x6 TLR with an 80mm, and to complicate things more also a 6x17 & 75mm Super Angulon. However it's easier in practice than it sounds, you rapidly get an instinct for framing & composing each format/lens and you don't think of what's equivalent to what while shooting, I frame each image intending to print full frame.

    Ian
     
  15. rthomas

    rthomas Member

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  16. Bruce Watson

    Bruce Watson Member

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    What Walter said.

    Changing from 35mm to 8x10 is sorta like changing from trumpet to sax. What you know about music (how to read, tonality, rhythm, etc.) carries over. However, what you know about how to physically play the trumpet is of little value in physically playing the sax.

    What you know about photographing with 35mm cameras is of limited use in using a view camera. This includes lens choice. While you can figure out and buy an "equivalent" lens for 8x10 from your 35mm days, you will likely not use it the same way, if at all.

    Don't confuse belief with the truth. Few who are in the process of making the transition believe the experiences of people who have made the transition before them. But that doesn't mean they aren't telling you the truth.