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Thread: Favorite aperture?

  1. #41
    Kirk Gittings's Avatar
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    Re: Favorite aperture?

    Quote Originally Posted by Doremus Scudder View Post
    Degradation due to diffraction is a direct physical result of the size of the aperture. It has nothing to do with lens design.

    Keep in mind, however, that even with rather stringent standards for the circle of confusion in the print, the effects of diffraction from a 4x5 negative (printed fairly full-frame) shot at f/45 will not be visible to the critical viewer until the prints are significantly larger than 16x20 inches. Even a 20x24 will not exhibit apparent degradation from diffraction unless the viewer is less than 18 inches or so from the print, much closer than "normal" viewing distance.

    Upshot: we can safely use very small apertures on 4x5 and still print fairly large without significant image degradation from diffraction. An 11x14 inch print from a negative shot at f/64 still has a diffraction-limited CoC of about 0.066mm, which is below the resolution powers of the eye at normal viewing distances.

    To answer the original question: I like f/32 on 4x5 a lot. It's my "go to" stop if I have any doubts about DoF issues and seems to be one I end up using most anyway. I measure focus spread and set aperture for optimum based on a CoC of 0.066mm. I don't have any qualms, however, about using f/64 if needed for DoF. I just make a note not to print that image too large.

    Given that most lenses designed for 4x5 use have their optimum aperture at f/22, and that diffraction degradation is not objectionable (for me at least) till f/45 or greater, the aperture range to use is a no-brainer. The only exception is for those who want out-of-focus areas in their prints and must use larger apertures, or even shoot wide-open. Lens aberrations at larger apertures are much more of a concern than diffraction however...

    Best,

    Doremus
    All absolutely true. In the old days when using very small apertures I would make a note to myself that I wouldn't print that particular image as large as I might otherwise. Now, diffraction is especially not much of an issue when printing digitally in whatever form as a slight touch increase in sharpening will effectively nullify visually any effect from diffraction.
    Thanks,
    Kirk

    "Vocation to Solitude -- To deliver oneself up, to hand oneself over, entrust oneself completely to the silence of a wide landscape of woods and hills, or sea, or desert; to sit still while the sun comes up over the land and fills its silences with light." Thomas Merton

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  2. #42
    Kirk Gittings's Avatar
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    Re: Favorite aperture?

    Quote Originally Posted by Old-N-Feeble View Post
    I don't really like the term "normal viewing distance". What is that, precisely? A 4x5 viewed at 10 inches? An 8x10 viewed at 20 inches... a 16x20 viewed at 40 inches? If so, then what's the point, barring presbyopia, of printing larger than 4x5? I want folks to be interested in a 120x240 inch print and be able to walk up to it and view fine detail. Okay... I can't carry a 12x20 camera these days but a 4x8 comes pretty close.
    If you ever go to many exhibits of LF images you will note that viewers literally put their nose on a print. I know I bring my reading glasses to such exhibits. Normal viewing distance for LF? No such thing.
    Thanks,
    Kirk

    "Vocation to Solitude -- To deliver oneself up, to hand oneself over, entrust oneself completely to the silence of a wide landscape of woods and hills, or sea, or desert; to sit still while the sun comes up over the land and fills its silences with light." Thomas Merton

    KIRK GITTINGS
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  3. #43

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    Re: Favorite aperture?

    Quote Originally Posted by Kirk Gittings View Post
    If you ever go to many exhibits of LF images you will note that viewers literally put their nose on a print. I know I bring my reading glasses to such exhibits. Normal viewing distance for LF? No such thing.
    Yeah -- but they are probably LF photographers...

    I have slipped in a magnifying glass into shows...LOL! I want people to come up to my images and explore all aspect of it...otherwise it is like driving the loop around Yosemite Valley with a video camera hanging out the window, and just looking at the scenery on the telly when one gets home.

  4. #44

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    Re: Favorite aperture?

    Quote Originally Posted by Vaughn View Post
    Yeah -- but they are probably LF photographers...

    I have slipped in a magnifying glass into shows...LOL! I want people to come up to my images and explore all aspect of it...otherwise it is like driving the loop around Yosemite Valley with a video camera hanging out the window, and just looking at the scenery on the telly when one gets home.
    Whenever I go to a museum I see folks craning ever-so-closely to whatever they're viewing to get a better CLOSER look. Folks will, indeed, get within inches of even the largest objects to get a better look... and want to reach out and touch... the UNtouchable.

  5. #45

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    Re: Favorite aperture?

    Quote Originally Posted by Corran View Post
    You know I always wondered about that. It made sense to me that it would depend on the relative size of the aperture.

    Thanks for your opinions Lenny. Like I mention, I feel like I've not seen a problem so lately I've been shooting at f/32 occasionally. I won't worry about it anymore.
    You're very welcome.... I would add that this is the easiest test in the world to do. We all have our processes set up. It's easy enough to expose a few extra sheets of film and shoot the same shot at different apertures. Then scan and print each one to see what happens. (Or print them in the darkroom, of course.)

    While I'm here, Brian, I didn't mean anything by it. Leigh, thanks four your comments, I would agree. I think that lens manufacturers have been fairly opaque with these kinds of details, or at least kept them very technical. When I looked into this for the Rodenstock lenses, all I could find was MTF (I think I have that acronym right). There wasn't a comparison of the different apertures. Maybe its just me...

    Anyway, informative discussion.

    Lenny
    EigerStudios
    Museum Quality Drum Scanning and Printing

  6. #46
    8x10, 4x5, ..., Tessina Leigh's Avatar
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    Re: Favorite aperture?

    Hi Lenny,

    Ordinarily, MTF curves are provided at two or three specific apertures (designated 'K' for no obvious reason).
    One K value is wide open, one is usually f/16 or f/22, and there may be a third.

    Performance at other apertures is left as an exercise for the student.

    MTF curves are published because they're very easy to generate automatically, by computer.
    There's no manual intervention required, except to set the aperture on manual lenses.

    You can't infer anything about diffraction from the MTF data by any technique known to me.
    Perhaps others know how to do it.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  7. #47
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    Diffraction is usually a smaller effect than inadequate depth of field. But inadequate DOF is often a smaller effect than subject movement in the longer exposures required by small apertures.

    I try to pay attention to the biggest effects first. If that limits print size, then that is a better outcome than an image that can't be printed at all.

    I don't have a favorite aperture, in the way I have a favorite ice cream flavor. For any given image, I have a favorite look, and that usually dictates the aperture. But always it is a dynamic balance between competing influences.

    Everybody gets that bit, but often I think people don't consider which of those influences have the most visible effects. Diffraction effects are usually the least significant.

    Rick "thinking aperture is an objective choice based on a subjective intention" Denney

  8. #48
    8x10, 4x5, ..., Tessina Leigh's Avatar
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    Re: Favorite aperture?

    Quote Originally Posted by rdenney View Post
    Diffraction effects are usually the least significant.
    Hooray.

    He Who Must Be Quoted and I actually agree for once.

    Diffraction is one of those boogeymen that parents use to frighten their kids into eating their broccoli.

    In the vast majority of images it's simply a non-issue.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  9. #49

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    Re: Favorite aperture?

    Quote Originally Posted by Lenny Eiger View Post
    You're very welcome.... I would add that this is the easiest test in the world to do. We all have our processes set up. It's easy enough to expose a few extra sheets of film and shoot the same shot at different apertures. Then scan and print each one to see what happens. (Or print them in the darkroom, of course.)

    While I'm here, Brian, I didn't mean anything by it. Leigh, thanks four your comments, I would agree. I think that lens manufacturers have been fairly opaque with these kinds of details, or at least kept them very technical. When I looked into this for the Rodenstock lenses, all I could find was MTF (I think I have that acronym right). There wasn't a comparison of the different apertures. Maybe its just me...

    Anyway, informative discussion.

    Lenny
    I didn't think you meant anything by it. It was just a very perplexing message since it purported to be in response to something I said but actually had nothing to do with anything I said.
    Brian Ellis
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    a mile away and you'll have their shoes.

  10. #50

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    Re: Favorite aperture?

    I don't have a favorite aperture, because aperture is dictated by the type of image I am trying to create.

    But I do have a favorite default aperture that I begin with for each image. I start at the lens' sharpest aperture. If that provides the DOF that I want, then that is ideal because I get to shoot at the lens' optimal aperture. But If I need more DOF, I stop down. If I need less DOF, I open up. Stopping down and opening up from the sharpest aperture both involve compromises in term of image quality. But the importance of DOF generally eclipses those compromises.

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