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  1. #11
    polyglot's Avatar
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    "Highly corrected" does not imply good bokeh at all, it just means that spherical aberration is well corrected. As it happens (over-)correction of SA tends to cause terrible bokeh and some of the prettiest bokeh you'll see comes from lenses with severely under-corrected SA. The SA causes the edges of the highlight discs to be softly rounded off; exactly correcting for SA results in sharp-edged bokeh and over-correcting SA (a common approach to getting a bit more sharpness) results in nisen-bokeh, i.e. line doubling because the edges of the highlight discs are brighter than their centres.

    If you want the ultimate in bokeh, you need to use an apodisation filter by the aperture, e.g. Minolta's 135 STF.

  2. #12

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    Quote Originally Posted by polyglot View Post
    If you want the ultimate in bokeh, you need to use an apodisation filter by the aperture, e.g. Minolta's 135 STF.
    So, "ultimate bokeh" means "almost completely featureless backgrounds"? It's kinda dull, actually.

  3. #13
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    In the end I don't do the sums, just look at a lens' image before deciding if I like it - But I still think overall balance of properties is more important than just sharpness

    I am surprised no one has attacked me for commenting on the properties of early Heliars

  4. #14

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    Grumpy... That's precisely what I'm doing. I'm making an overall observation that very round apertures make better images (stopped down a bit) than octagonal ones. Lately, that's become very obvious to me. Though, lately, my powers of observation and logic are weak.

  5. #15
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    And the reason you've splattered this same nonsense across (at least) three different fora is ______?

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  6. #16
    polyglot's Avatar
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    If you shoot 35mm, have a look at some images from a CZJ Flektogon 35/2.4. Hexagonal (and very obviously so) aperture, but still beautiful bokeh; for example (digital photos of no artistic merit, but nevertheless an illustration of the lens).

  7. #17

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    I thought 'bokeh' was just a word you slipped into the title on eBay to try and get a better price for your lens.


    .... like 'petzval'.
    Steve

  8. #18
    John Austin's Avatar
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    Quote Originally Posted by polyglot View Post
    "Highly corrected" does not imply good bokeh at all, it just means that spherical aberration is well corrected. As it happens (over-)correction of SA tends to cause terrible bokeh and some of the prettiest bokeh you'll see comes from lenses with severely under-corrected SA. The SA causes the edges of the highlight discs to be softly rounded off; exactly correcting for SA results in sharp-edged bokeh and over-correcting SA (a common approach to getting a bit more sharpness) results in nisen-bokeh, i.e. line doubling because the edges of the highlight discs are brighter than their centres.

    If you want the ultimate in bokeh, you need to use an apodisation filter by the aperture, e.g. Minolta's 135 STF.
    Hang on, what I actually typed was "I understand it is a function of the way spherical aberration is corrected, or not" - I have added the bold type

  9. #19

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    Okay... if "some" spherical aberration is necessary to produce nice bokeh then maybe I should be looking for Imagons, SF Ektars, SF Fujinons, etc. I'd only use the discs with the periferal holes closed though. I hate the effect created with them open. I'd definitely use them "stopped down" a bit. Am I crazy or is this one way to get what I want?
    Last edited by Old-N-Feeble; 04-03-2012 at 12:58 PM. Click to view previous post history.

  10. #20

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    RE: front aperture. Doesn't that degrade image quality in other ways? I thought the aperture needed to be placed precisely at the nodal point. Also, that method wouldn't work with lenses of shorter-than-normal focal length would it? Maybe I'll give it a try.

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