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Thread: DIFF? "Fast" vs "Slow" lens at Small Apertures?

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  1. #1

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    Question DIFF? "Fast" vs "Slow" lens at Small Apertures?

    Hi, All,

    All things being equal, will a "fast" lens provide a better or different image from a "slow" lens, at smaller apertures.

    For example, two 150 mm lenses, both set at aperture of f22 or smaller, will the "faster" lens provide a different image? Like greater depth of field? More clarity? Anything different?

    My apologies for this basic question, but I did search. I know a "fast" lens can open up wiiiide for low light, small DOF images...

    Thank you in advance for your help!



    Robt.
    Robt.

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  2. #2

    Re: DIFF? "Fast" vs "Slow" lens at Small Apertures?

    There will be different image characteristics due to different lens designs but no difference in the fundamentals like DOF etc. If anything, some really fast lenses might be optimized for wide open use rather than closed down, so the slower lens might perform a tad better at smaller apertures but I doubt it would be anything significant.

  3. #3
    Format Omnivore Brian C. Miller's Avatar
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    Re: DIFF? "Fast" vs "Slow" lens at Small Apertures?

    Case in point, Schneider Xenar 6.1/210mm and Xenar 4.5/210mm. Similar lenses, and similar performance. The main difference seems to be weight. I'm sure on a lens test you wouldn't be able to tell one from the other.

  4. #4
    hacker extraordinaire
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    Re: DIFF? "Fast" vs "Slow" lens at Small Apertures?

    The main difference seems to be weight, and ease of focusing (due to bright ground glass with a fast lens).
    Science is what we understand well enough to explain to a computer. Art is everything else we do.
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  5. #5
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: DIFF? "Fast" vs "Slow" lens at Small Apertures?

    Lens design is an extraordinarily complex process, with numerous tradeoffs to achieve the desired performance.

    As you increase the full aperture, the distortion and aberrations become ever more difficult to control.

    A lens like the Nikkor 58mm f/1.2 Nocturnal is designed to be used wide open, and would perform a bit differently than a 58mm lens of smaller aperture.

    But the differences would be difficult to detect in normal use, being more of an academic or laboratory exercise.

    - Leigh

  6. #6
    ic-racer's Avatar
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    Re: DIFF? "Fast" vs "Slow" lens at Small Apertures?

    Look at some examples here. That is the only way to answer the question, by example. http://www.hevanet.com/cperez/testing.html For example, various lenses for 8x10 and larger formats may have big differences in edge sharpness at F22.

    If you want a generalization then, the smallest aperture on a lens in almost every case will dictate both depth of field and sharpness, irrespective of the lens.

  7. #7

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    Re: DIFF? "Fast" vs "Slow" lens at Small Apertures?

    I had a 135/3.5 Xenotar. It made a soft but pleasing image at f/3.5. At f/5.6 and smaller it just made a softer, crappier image than a good modern Symmar or Sironar.

    Same with the Aero-Ektar I had. It was great to get an image at f/2.5 with a 4mm depth of field. But at f/8 it was just a crap lens compared to a common $250 Rodenstock/Schneider/Fuji/Nikon 180mm.

    I'd only use those lens wide open, otherwise they are a waste of money. In fact, they probably are a waste of money period since it's just a hipster trend.

  8. #8

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    Re: DIFF? "Fast" vs "Slow" lens at Small Apertures?

    Frankie, it really depends on the lenses.

    For example, my 4"/2.0 TTH beats my 101/4.5 Ektar at all apertures down to f/16, which is as far down as it goes. Fine, wonderful, except that the 101 Ektar is better than good enough, is much smaller and lighter, and is in shutter so can be used for timed exposures slower than 1/30, my 2x3 Speed's focal plane shutter's slowest speed. Guess which one I use more.

  9. #9

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    Re: DIFF? "Fast" vs "Slow" lens at Small Apertures?

    Thanks for all the input, folks!

    My reason for asking...if a person never uses a lens "wide open" to its largest aperture... then is there ANY image benefit of a fast lens over a slow lens, when using tiny apertures to maximize depth of field.

    I find much discussion of fast lens used "wide open" in low light settings, but does a fast lens help at all in low light settings with tiny apertures?

    Thank you!

    Robt.
    Robt.

    Work, Work, Work, Work.....Landscapes

    WidePan 120; Hasselblad XPAN; Pentax 20D;

  10. #10

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    Re: DIFF? "Fast" vs "Slow" lens at Small Apertures?

    Quote Originally Posted by Mr_Toad View Post
    Thanks for all the input, folks!

    My reason for asking...if a person never uses a lens "wide open" to its largest aperture... then is there ANY image benefit of a fast lens over a slow lens, when using tiny apertures to maximize depth of field.

    I find much discussion of fast lens used "wide open" in low light settings, but does a fast lens help at all in low light settings with tiny apertures?

    Thank you!

    Robt.
    The larger aperture does help in low light situations while focusing. For me, every little bit of extra light helps.

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