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Thread: quick ?

  1. #1
    Rising Star
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    quick ?

    image jump = the difference in bifocal dimensions? ex:35x22 1/2 of 35 and the sum subtracted from 22?

  2. #2
    Master OptiBoarder lensgrinder's Avatar
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    Image Jump = Add power X Seg Center

    Seg Center = Seg Depth - 1/2Seg Width

  3. #3
    Rising Star
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    ok let's say 2.50 add ft35 35x22 2.5x4.5/10 ? is that right or would it be 2.5x17.5/10

  4. #4
    Master OptiBoarder lensgrinder's Avatar
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    Seg Center = 22 - (35/2)
    Seg Center = 4.5mm

    Now use Prentice's Rule
    P = 0.45cm X 2.5
    P = 1.13^ which is also called image jump

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