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Thread: Wide open?

  1. #31
    Rol_Lei Nut's Avatar
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    Quote Originally Posted by Aristophanes View Post
    The tradeoffs inherent to the physics of optics are usually mitigated by increasing the size of elements across the axis, added elements, better coatings, etc. A major tradeoff is mass. For many brands a 50/2 is almost 30% less weight than a 50/1.4, and usually less than half the price, with both having near equal sharpness and distortion at f/2.8.

    I had a Zeiss 50 for my Pentax system. It had superb center sharpness and resolution and great colour rendering. Its edge distortions were noticeable until 2 stops down from max. It was also worth 2.5x more than a Pentax brand equivalent but in real life photos, it was hard to see the differences. It had great all around performance, but there was a flaw based on the unavoidable optical physics limitations. I could get the same performance out of much less expensive glass at the expense of 1-stop.

    I therefore concluded biggest discrepancy is price vs. noticeable distortion in real life photos.
    A conclusion based on a sample of one?!!?

    I think the key word you used is "usually": while faster lenses often (usually) do have to compromise some performance aspects, the best ones manage to touch several sweet spots...
    M6, SL, SL2, R5, P6x7, SL3003, SL35-E, F, F2, FM, FE-2, Varex IIa

  2. #32
    Aristophanes's Avatar
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    Quote Originally Posted by Rol_Lei Nut View Post
    A conclusion based on a sample of one?!!?

    I think the key word you used is "usually": while faster lenses often (usually) do have to compromise some performance aspects, the best ones manage to touch several sweet spots...
    Yes, they do. But the laws of physics demand all lenses have tradeoffs, especially wide open. It is unavoidable. Look and ye shall find.

    If there weren't all manufacturers would gravitate towards an identical design.

  3. #33
    Rol_Lei Nut's Avatar
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    Quote Originally Posted by Aristophanes View Post
    Yes, they do. But the laws of physics demand all lenses have tradeoffs, especially wide open. It is unavoidable. Look and ye shall find.

    If there weren't all manufacturers would gravitate towards an identical design.
    The main tradeoff for manufacturers (and consumers) is often cost. The fast lenses with good allround performamance are usually expensive.
    M6, SL, SL2, R5, P6x7, SL3003, SL35-E, F, F2, FM, FE-2, Varex IIa

  4. #34
    keithwms's Avatar
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    Ah physics

    Anyway, the basic point, for those who care to know, is that lens design issues tend to reduce resolution at wide apertures, whereas diffraction tends to reduce performance at small apertures. Thus the best performance is typically at intermediate apertures. For RF lenses, the best performance is often seen a stop or two wider open than for SLRs. But that difference is rapidly disappearing now, with all the fancy aspherical corrections etc., assuming you can afford them. Which is a big "if" for those not earningsteady income from their photography.

    What constitutes "best performance" is certainly open for interpretation. What you typically see is center performance at or near its very best when the lens is stopped down a small amount (a stop or two or three) while corner performance is often lacking until ~f/8. When people speak about performance overall, they tend to mean some sort of average across the frame and across all the frequencies. For that reason, the concept of best performance is really never going to sit well with everyone. We all have different needs and preferences.

    My [very] broadbrush observation is that RF shooters tend to be a bit biased toward the center performance... due to the focusing mechanism. Whereas SLR users tend to be biased towards the third lines. So when people speak of high performance, it helps to keep these things in mind: how you tend to frame, and what frequency info is important... not to mention colour rendition, which is another subject entirely, since MTF charts are usually shot at one wavelength or two.

    At the end of the day, as has been said many times before, you just have to experiment and go with your gut instinct. Its not worthwhile to sweat minor technical details such as only getting 70% performance wide open at the edge of a frame. Most lenses out there will do marvelous rendition, where it matters most, at all reasonable apertures.

    If it were possible to quote performance per dollar, the contax G lenses would win, hands down. By a long shot.
    "Only dead fish follow the stream"

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  5. #35
    Aristophanes's Avatar
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    Quote Originally Posted by Rol_Lei Nut View Post
    The main tradeoff for manufacturers (and consumers) is often cost. The fast lenses with good allround performamance are usually expensive.
    Cost. Substantially:

    http://www.bhphotovideo.com/c/produc...ummilux_M.html

    $3,995

    http://www.flickr.com/photos/28753682@N06/6005248119/

    http://www.bhphotovideo.com/c/produc...0mm_f_1_4.html

    $359.95

    http://www.flickr.com/photos/kaherdin/6286544413/

    Worth 8x the price and 40% more weight?

    OK. I am comparing marketing extremes, which is fun

  6. #36
    keithwms's Avatar
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    Bah.... Nikon 50/1.2, $450, and worth every penny.
    "Only dead fish follow the stream"

    [APUG Portfolio] [APUG Blog] [Website]

  7. #37
    zsas's Avatar
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    ^My dream lens (and I don't even own a Nikon....)
    Andy

  8. #38
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    Quote Originally Posted by keithwms View Post
    Bah.... Nikon 50/1.2, $450, and worth every penny.

    I will both second and third that. That was my glass investment for the year, and nothing has looked or felt better since.
    In other worlds he has
    darker days, blacker swells.
    Strokes that mix noir revenge
    on waves of grey.

  9. #39
    Aristophanes's Avatar
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    Quote Originally Posted by keithwms View Post
    Bah.... Nikon 50/1.2, $450, and worth every penny.
    http://www.bhphotovideo.com/c/produc...0mm_f_1_2.html

    $699.95 new.

    http://www.flickr.com/photos/patrick...n/photostream/

  10. #40
    keithwms's Avatar
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    See I praise something and its value goes up, interesting how that works!

    I bought it for $420 a couple years ago.
    "Only dead fish follow the stream"

    [APUG Portfolio] [APUG Blog] [Website]

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