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Thread: What kind of lens has aperture scale in mm?

  1. #11
    Mark Sawyer's Avatar
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    Re: What kind of lens has aperture scale in mm?

    Quote Originally Posted by Matt Stage View Post
    The Tri Tran Signature Pictorialist Lens is a casket system with meniscus lens elements available in focal lengths from 9" to 30". To address this issue, the aperture scale is marked in Roman numerals from I to VI.
    I think I remember reading about the Roman Pictorialists in Newhall's The History of Photography...
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  2. #12

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    Re: What kind of lens has aperture scale in mm?

    Quote Originally Posted by Matt Stage View Post
    The Tri Tran Signature Pictorialist Lens is a casket system with meniscus lens elements available in focal lengths from 9" to 30". To address this issue, the aperture scale is marked in Roman numerals from I to VI.

    Attachment 197659

    More info about this lens is ate the website: https://www.tritranphotography.com/tt-signature-lens
    Silly semantics alert!

    I'd always that that casket sets were a collection of cells that could be singly or in pairs as desired. Each cell is claimed to be a fully corrected anastigmat. If I understand Tri Tran's product slate correctly, all of his lenses are single element meniscii and he sells barrels in which meniscii of various focal lengths can mounted, one at a time. This doesn't seem to be quite the same as combining cells to make fully corrected double anastigmats or even switching single multi-element cells in a barre.

  3. #13
    Mark Sawyer's Avatar
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    Re: What kind of lens has aperture scale in mm?

    Quote Originally Posted by Dan Fromm View Post
    This doesn't seem to be quite the same as combining cells to make fully corrected double anastigmats or even switching single multi-element cells in a barrel.
    And that's what makes it a "Signature Pictorialist" lens! Silly photographers, always wanting well-corrected lenses...
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  4. #14

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    Re: What kind of lens has aperture scale in mm?

    Quote Originally Posted by Mark Sawyer View Post
    I figured you'd know it already, Pere, but some here may not. Your comment was just the perfect lead-in to my point.
    I didn't know and still don't understand. Could anyone of you who does please elaborate what this is about? I feel like being on the sideline of some very private joke.
    Expert in non-working solutions.

  5. #15
    Mark Sawyer's Avatar
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    Re: What kind of lens has aperture scale in mm?

    One of the basics of photography: the f/stop is determined by dividing the focal length by the aperture's diameter as measured through the front element, (aka "entrance pupil").

    When pjd mentioned casket sets (a barrel with multiple interchangeable elements for different focal lengths) being marked in mm, and Pere asked "if the aperture in mm is the real hole or if it is the effective hole size, seen from the front, to give the value that's used in the f/ calculation", I just pointed out that different cells would render different effective aperture sizes, which Pere had said a little less directly.

    The manufacturers' aperture scales always give f/stop values for infinity. For those of us who frequently work at close enough distances to need to factor in a longer focal length (bellows extension), having a scale marked in effective aperture diameter would be a more convenient way to figure exposures than converting from infinity-based f/stops.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  6. #16

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    Re: What kind of lens has aperture scale in mm?

    I mounted a Zeiss Protar VII set and made some measurements. The mm scale on the barrel reflects the physical aperture (how could one scale compensate for different cells, if cells of differing power really make much of a difference to effective aperture). With a 48cm cell up front the aperture apparent through the front element appears less than 1mm different to the physical aperture as shown on the scale. Measuring through the front element is quite tricky, I think this is close enough to be workable.

    Zeiss did distribute tables with casket sets showing the aperture in mm required for a given f stop with various combinations of cells, maybe they adjusted these slightly to account for effective aperture rather than actual mechanical aperture. I don't think fractions of a mm make enough of a difference to worry about - my exposures generally come out well enough, and when they don't it's not Carl Zeiss and their mm aperture scale to blame.

  7. #17

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    Re: What kind of lens has aperture scale in mm?

    Quote Originally Posted by Mark Sawyer View Post
    The manufacturers' aperture scales always give f/stop values for infinity. For those of us who frequently work at close enough distances to need to factor in a longer focal length (bellows extension), having a scale marked in effective aperture diameter would be a more convenient way to figure exposures than converting from infinity-based f/stops.
    Ok, got it. It's another way to do bellow compensations.
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    Re: What kind of lens has aperture scale in mm?

    Quote Originally Posted by Havoc View Post
    Ok, got it. It's another way to do bellow compensations.
    It's calculating your actual f/stop, not compensating for an incorrect f/stop.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

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    Re: What kind of lens has aperture scale in mm?

    Quote Originally Posted by Mark Sawyer View Post
    It's calculating your actual f/stop, not compensating for an incorrect f/stop.
    Surely you meant effective.

  10. #20
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    Re: What kind of lens has aperture scale in mm?

    Quote Originally Posted by Dan Fromm View Post
    Surely you meant effective.
    The difference being?

    I think if an f/stop is the ratio of focal length to aperture diameter as measured through the entrance pupil, that would be both the actual and the effective f/stop. But I'm willing to be educated...
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

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