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Thread: Optimized aperture

  1. #1

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    Optimized aperture

    Where can I find the information of optimized aperture of certain lens? Is it always f22? I remember seeing Docter 240 optimized at f 16, and Rodenstock Apo sironar s series optimized at f 16. How about nikon M series, fuji C series, and fuji A series?

  2. #2

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    Re: Optimized aperture

    you can shoot them wide open, and they would still be sharp. it's a matter of how much DOF you want.

  3. #3
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    Re: Optimized aperture

    Probably varies with application, although your question is surely directed toward pictorial use in the field.

    I think f/22 is probably fairly consistent for graphic arts process lenses. With those lenses often being in the f/9 range (except for very long f.l. ones), that suggests more than 3 stops down from wide open.

    Smaller format lenses it's common for roughly 2 stops down from wide open to be 'best'. (Someone told me Kodak Medalist Ektar f/8-11 despite being f/3.5 wide open).

    Tessars f/11 or higher to keep corners sharp, but don't know where resolution is best.

    Application-specific special lenses like certain aerial recon lenses supposedly optimal (or maybe 'as good as') wide open. Projection lenses and point source enlarging lenses are used wide open (maybe for other reasons, and may not even have an adjustable aperture).

    Sounds like you're an LF person anyway (you're here, and the lenses you asked about sound like it too), so you're probably aware format plays some role. 35mm would be into diffraction limits probably at f/22.

    I have a monochromatic 15"x21" format graphic arts lens that is f/8 max and was told for that particular lens f/9.5 was the 'sweet spot'.

    Probably not what you were asking for, but hopefully something of interest.

    Murray

  4. #4

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    Re: Optimized aperture

    You may get all sorts of anwers. I've heard guys say"just stop it down as far as you can get way with" which is fine for magazine publication or contact prints in some cases but i don't know many who make a living shooting that way. There's a chart on the net somewhere with lens test data that a couple guys did. I googled and found this:
    http://www.hevanet.com/cperez/testing.html
    it shows center and edge sharpnes at various apertures. it should give you an idea.

  5. #5

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    Re: Optimized aperture

    "optimized aperture" is meaningless when a good lens can give you the same 60 lp/mm from wide open at f/4.5 down to f/22. beyond that, diffraction limits resolution.

  6. #6

    Re: Optimized aperture

    Seems like many modern lenses, going by results from C. Perez (et al), is near f16. In theory, shooting more wide open could get better results, though I think lens construction limits that on many lenses. My personal choices (with 4x5) is to shoot at f11 or f16, though I have shot wide open or f8 quite often. Many times either selective focus or a desire to have more in focus, dictates my choice in aperture.

    Ciao!

    Gordon Moat Photography

  7. #7

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    Re: Optimized aperture

    The aperture is related to the focal-lenght, f/x, so the with longer focal-lenghts the aperture can be smaller with longer lenses before diffraction influences the image. Up to the fourties of the last century LF lenses where optimized for f/22, but later the optimum diaphragm was, and is, f/16. Diffraction optimized lenses, such ones used for micro-electronis, work at best wide open. But with normal lenses on can correct small residual faults by stopping down the diaphragm.

    Try it with your lens, it's the easiest way to find out.

  8. #8

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    Re: Optimized aperture

    Quote Originally Posted by Songyun View Post
    Where can I find the information of optimized aperture of certain lens? Is it always f22? I remember seeing Docter 240 optimized at f 16, and Rodenstock Apo sironar s series optimized at f 16. How about nikon M series, fuji C series, and fuji A series?
    Lens test data at f11, f16 and f22:

    http://www.hevanet.com/cperez/testing.html

  9. #9

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    Re: Optimized aperture

    Folks:
    Roughly a year ago View Camera magazine had a couple of articles by Robert Hallock who showed how one can calculate this. The basic idea is that as the aperture gets smaller, things like spherical aberation get better but at some point diffraction takes over and dominates. Typically f16-22 is best for many LF lenses but he shows how to calculate it exactly.
    Cheers,
    Dave B.

  10. #10

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    Re: Optimized aperture

    My APO Symmar 210mm is sharpest at f 11 but I can very seldom use f 11 because I need more DOF!
    So always stop so much down as you need to!

    Cheers Armin

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