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Thread: Axis query.

  1. #26
    OptiBoardaholic
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    Most sv lenses had the cyl on the front even the first generation plastic lenses followed the norm of the time with front cylinders. All bifocals except some Ultex style had the cyl on the back. Rx’s were written with + cyl because that is what was taught in school to the ophthalmologist’s who only used a trial frame for refractions O.D. Used a phoropter so they refracted in minus cyl form.

  2. #27
    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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    Enlightenment from an expert~ Thanks!!!

  3. #28
    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
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    Quote Originally Posted by Uncle Fester View Post
    "Am I remembering correctly from opticians school when we learned plus cyls were written by doc's because early glass spectacle lenses always had the cyl generated on the convex ("plus") side of the lens?"

    Can any old timers verify this memory?
    Yes, cylinders were ground on the front because..

    Empirical wisdom—before Zeiss pioneered mathematical calculations in lens design—had found that keeping the back curve of a lens near -6.00 produced sharpest peripheral images…up to that point.

    B

  4. #29
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    Quote Originally Posted by Barry Santini View Post
    Yes, cylinders were ground on the front because..

    Empirical wisdom—before Zeiss pioneered mathematical calculations in lens design—had found that keeping the back curve of a lens near -6.00 produced sharpest peripheral images…up to that point.

    B
    And it was much easier to grind a sphere on the back. I remember standing over the sphere bowl all day fining and polishing spheres. It may also have been much cheaper to make the sphere machines than the cylinder machines and until we had generators we had to "rock the cylinder in by hand. NOT FUN.

  5. #30
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    Don't you miss the bleeding finger tips from the coarse emery?

  6. #31
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    Quote Originally Posted by Fluegge Optical View Post
    Don't you miss the bleeding finger tips from the coarse emery?
    Or the blisters from the hot blocks and lenses with the pitch blocking.
    Generating oil flaring up cutting photograys. We could go on and on.

  7. #32
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    Sadly still doing that stuff, with "specials" and Rede Rites in plastic, and some crazy saddlebacks!

  8. #33
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    Quote Originally Posted by Fluegge Optical View Post
    Sadly still doing that stuff, with "specials" and Rede Rites in plastic, and some crazy saddlebacks!
    I thought that saddlebacks would be gone with the dinosaurs since cornea surgery has advanced so much.

  9. #34
    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
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    Quote Originally Posted by finefocus View Post
    I thought that saddlebacks would be gone with the dinosaurs since cornea surgery has advanced so much.
    Back in my San Diego days, my job was to grind, edge and mount dive mask lenses. Every job was custom. Too many saddlebacks to mention. All glass. Aluminum oxide, cerium oxide, Pella oil and epoxy. And I still have all of my digits……..needless to say, I no longer do dive masks.
    I bend light. That is what I do.

  10. #35
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    I would guess most members of this forum don’t even know what a saddleback curve looks like. Old timers don’t answer let’s see what what the young folks have to say. Todays generators can actually grind a saddleback making life easier when you have no ther choice.

  11. #36
    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
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    Quote Originally Posted by Lensman11 View Post
    I would guess most members of this forum don’t even know what a saddleback curve looks like. Old timers don’t answer let’s see what what the young folks have to say. Todays generators can actually grind a saddleback making life easier when you have no ther choice.
    I was grinding saddlebacks on a 113, and occasionally on a 108. Let’s see how many ‘younguns’ understands…..
    I bend light. That is what I do.

  12. #37
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    Darned few I'm sure...Not many of us ole timers left!

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