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  1. #1
    Resident Heretic Bruce Watson's Avatar
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    spherical aberration solved?

    Looks like the 2000 year old question of how to eliminate spherical aberration in camera lenses might actually be solved.

    Some of you are good at lens math. What say you?

    [EDIT]
    Looks like this is old news from last year. Well, maybe someone will find it interesting. Has this been reported on LFP.info before? If so I must have missed it.
    [/EDIT]

    [EDIT_2]
    Published in Applied Optics, they'll let you read the abstract for free anyway.

    If you can make a singlet lens that's free of spherical aberration it would seem you could eliminate some elements in a view camera lens, making it sharper, lighter weight, and cheaper. If anyone were still making large format lenses that is. Maybe Cooke will make some just for fun as they have done before.

    But even if they did, and this eliminated some of the sharpness problems of shooting wide open, would we? Shoot wide open I mean. Because in LF, there are other reasons to stop down. But more choice would be better than less choice, yes?
    [/EDIT_2]

    Bruce Watson

  2. #2
    Kevin Kolosky
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    Re: spherical aberration solved?

    I have to start eating more bread with Nutella spread on it!

  3. #3
    ic-racer's Avatar
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    Re: spherical aberration solved?

    Click image for larger version. 

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  4. #4

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    Re: spherical aberration solved?

    IMHO spheric aberration cannot be considered as the single factor, because we also want field flatness, low distortion, to correct primary and secondary chromatic aberrations, low fall-off... we also want the lens to work well for a range of magnifications... and we also may want a good bokeh...

    That paper should have importance for scholars, but IMHO it is no industrial revolution, it's an analytical method... but I'd say that current designs are optimized with software.

    Of course aspheric surfaces are useful to correct spheric aberration, but manufaturing high quality aspheric surfaces has been industrially challenging, what is an industrial revolution is the way that manufacturing has improved, specially in costs.

    An remarkable industrial leap forward was compound aspherical elements. In the cheapo (now old) Nikon 28-80mm 3.3-5.6 kit lens the front element is a compound aspherical. "This means Nikon glues a thin plastic corrector over another spherical glass element". The result was an atonishing performance in a crazy cheap lens made in mass production conditions.

    https://kenrockwell.com/nikon/28-80mm-g.htm


    Amazigly, manufacturers don't play care in the important/easy things, like a round iris or the spheric aberration correction strategy in the OOF that delivers a pleasing bokeh.


    This gives an advantage to true LF artists, they have little competition when beauty counts because they have the true good glass for capturing beauty. Today industry is too focussed in dxo ratings and sadly ignoring beauty.

  5. #5
    Mark Sawyer's Avatar
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    Re: spherical aberration solved?

    For all practical purposes, spherical aberration was eliminated by WWII or earlier. This is sort of like someone saying they've just designed the first apochromatic lens.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  6. #6
    Resident Heretic Bruce Watson's Avatar
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    Re: spherical aberration solved?

    Quote Originally Posted by Mark Sawyer View Post
    For all practical purposes, spherical aberration was eliminated by WWII or earlier. This is sort of like someone saying they've just designed the first apochromatic lens.
    Not with a singlet -- a single piece of glass. It always took at least two, which is perhaps why lenses of the period used so many cemented doublets and triplets.

    What makes this interesting to me is that it can be done with a singlet. Which should allow replacement of a cemented doublet or triplet with a singlet, which should result in a lighter and physically smaller camera lens. Not to mention somewhat better light transmission because of less glass, and less internal reflections because of fewer surfaces, etc. And of course it might be cheaper as well, because less glass even if the singlet is more expensive to make.

    So... lighter, smaller, faster, cheaper. What's not to like?

    Bottom line for me is that I could hike farther, and make photographs where I could not before. And others like me could do the same. And that, might make it worth doing. IDK.

    And lets not leave out the fun of solving an "unsolvable" problem.

    Bruce Watson

  7. #7
    Mark Sawyer's Avatar
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    Re: spherical aberration solved?

    Quote Originally Posted by Bruce Watson View Post
    So... lighter, smaller, faster, cheaper. What's not to like?
    The distortion, curved field, chromatic aberration and coma. Zeroing out one aberration at the expense of ignoring others may be an interesting math problem, but not a practical solution to anything.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  8. #8
    Resident Heretic Bruce Watson's Avatar
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    Re: spherical aberration solved?

    Quote Originally Posted by Mark Sawyer View Post
    The distortion, curved field, chromatic aberration and coma. Zeroing out one aberration at the expense of ignoring others may be an interesting math problem, but not a practical solution to anything.
    This is the difference between science and engineering. Science is about figuring it out, engineering is about using it to build things. The scientists in this case have figured out how to solve spherical aberration in a singlet. Good on 'em. Really, they've done great work here.

    Engineers haven't yet used this to design lenses AFAIK. Maybe the optical engineers will eventually, maybe not. But if they do, my bet is this will show up first in cell phone cameras, not lenses for us. It may never show up in lenses for LFers.

    Bruce Watson

  9. #9
    Nodda Duma's Avatar
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    Re: spherical aberration solved?

    Incorrect. In fact, spherical aberration can be corrected with a single surface. Sir Isaac Newton corrected spherical aberration, lateral color, spherochromatism, astigmatism, and distortion with the paraboloidal surface in the 1600s.

    The single lens of a CD reader corrects spherical aberration entirely.

    Pere is right, this was a well-known academic problem and good for him solving it, but it is purely academic. The physicist worked out a mathematical solution — which is great — for a problem that is solved via other methods every day by lens designers. That’s a great way to earn his doctorate. But in reality it can actually take longer to set up the initial conditions in Zemax or Code V than to run the optimization itself that drives sph ab to zero ..which is not much faster for a simple lens than doing the Seidel coefficient calculations by hand.

    So leading to cheaper, simpler solutions... I shudder at the thought of trying to convince an optical shop to turn a surface like that, or even a molded optics shop to do the same. More expensive and more complex.. definitely.

    Not knocking what he did, don’t get me wrong. I have issue with the sensationalist misleading reporting that followed. It is just a bit too much.




    Quote Originally Posted by Bruce Watson View Post
    Not with a singlet -- a single piece of glass. It always took at least two, which is perhaps why lenses of the period used so many cemented doublets and triplets.

    What makes this interesting to me is that it can be done with a singlet. Which should allow replacement of a cemented doublet or triplet with a singlet, which should result in a lighter and physically smaller camera lens. Not to mention somewhat better light transmission because of less glass, and less internal reflections because of fewer surfaces, etc. And of course it might be cheaper as well, because less glass even if the singlet is more expensive to make.

    So... lighter, smaller, faster, cheaper. What's not to like?

    Bottom line for me is that I could hike farther, and make photographs where I could not before. And others like me could do the same. And that, might make it worth doing. IDK.

    And lets not leave out the fun of solving an "unsolvable" problem.
    Newly made large format dry plates available! Look:
    https://www.etsy.com/shop/Pictoriographica
    .. because my wife is happy when I can cover my photography expenses!

  10. #10
    Jac@stafford.net's Avatar
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    Re: spherical aberration solved?

    Quote Originally Posted by Nodda Duma View Post
    Incorrect. In fact, spherical aberration can be corrected with a single surface. Sir Isaac Newton corrected spherical aberration, lateral color, spherochromatism, astigmatism, and distortion with the paraboloidal surface in the 1600s.
    Half of a regular paraboloid is shown in the picture below. It is an interesting feature from nature.

    For a news story in 1973 I photographed Prof. Riccardo Levi-Setti, University of Chicago, holding a hollow spun aluminum cone-like shape (no lens!) which uses the dimensions of a crab's (or trilobite) eye. It is a poor print reproduction which does not show that at the small end is a cup of water very quickly brought to a boil, even through a dirty window on a bright overcast day.

    He found the dimensions using a scanning ion microscope to discern one cone of a crab's eye
    Picture here.

    More about the professor.

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