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Thread: Completely scientific explaination for bokeh

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    Senior Member RichA's Avatar
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    Completely scientific explaination for bokeh

    I figure someone must have one somewhere? You grind a lens, keep aberrations under control. Coma, astigmatism, spherical aberration and to a lesser extent, distortion and aperture shape must all play a part in the representation of out of focus areas. But has anyone linked specific corrections to what we see? Broadly, what produces the best bokeh, a highly corrected lens, or a poorly correct one?

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    Senior Member aleksanderpolo's Avatar
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    Re: Completely scientific explaination for bokeh

    You might have already read this:

    http://www.zeiss.com/c12567a8003b58b...2576fe004877fb

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    Senior Member kds315's Avatar
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    Re: Completely scientific explaination for bokeh

    Highly recommended Dr Hubert Nasse's explanation, yet very scientific.

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    Bokeh and MTF charts

    The discussion linked below teaches how to read MTF charts, making a helpful point about bokeh. You know how the charts have pairs of curves, one solid and one broken? The writer explains them and says that the closer together the curves, the smoother the bokeh.

    http://www.luminous-landscape.com/tu...ding-mtf.shtml

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    Senior Member RichA's Avatar
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    Re: Completely scientific explaination for bokeh

    Quote Originally Posted by aleksanderpolo View Post
    Thank you!

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    Re: Completely scientific explaination for bokeh

    It is an interesting link, I think Vivek posted it before in the bokehthread.
    Klaus is right it is far more scientific then this sentence promises; " Donít worry - Aside from some simple exceptions we will not be talking about mathematical formulas at all. "

    The following I found interesting because I was always curious about the circular lines in the big OOf fighlights - the more scientific among us probably knew this - ; " It is possible to recognise from this that the lens has a aspherical surface as these surfaces are often not smooth as a conventionally polished lens. Particularly in the cases of lenses which are manufactured by pressing hot liquid glass it is possible to recognise the traces of the turning process with which the mould was manufactured."

    Here is an example of this effect with the Canon Fd L 85/1.2

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    Re: Completely scientific explaination for bokeh

    Superb illustration of rough aspheric surface creating the "rings OOF" highlights, Michiel!

    (Lovely capture as well! )

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    Senior Member RichA's Avatar
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    Re: Completely scientific explaination for bokeh

    Quote Originally Posted by Vivek View Post
    Superb illustration of rough aspheric surface creating the "rings OOF" highlights, Michiel!

    (Lovely capture as well! )
    God, don't remind me. I had a 14" (wide) telescope with a screwed-up aspherical surface like that. Was a nightmare to try to rectify the situation. With telescopes, it really matters because you end up using the scope at effective focal lengths of 25,000-50,000mm or more and those optical problems cause havoc with the image.

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