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Thread: HELLLP! needed all the way from the UK

  1. #1
    OptiBoard Novice
    Join Date
    Nov 2017
    Dispensing Optician

    HELLLP! needed all the way from the UK

    Hi to all,

    I have a question I'm hoping you experts can answer, in the UK we seem to have huge lacking of any optical forum boards......
    In my practice, we are restricted to dispensing blue tints any darker than 72%LTF/ 18% absorption, my question is.....

    Where the figure of 72%LTF has been calculated from, I'm assuming an equation has been done at some point to come to that figure, but i cant find it anywhere.........

    And also what specific impact does it have on traffic light recognition.

    Many thanks to all you clever people who answer.

  2. #2
    Ghost in the OptiMachine Quince's Avatar
    Join Date
    Jan 2016
    Sebago ME
    Optical Laboratory Technician
    I think a lot of labs have samples of the densities either made by hand or acquired from lens distributors.

    Here are some examples if you are lacking samples:
    Click image for larger version. 

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    Click image for larger version. 

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    The recommended limitations are set so that the average eye will not be hindered to read while protected from harsh light, but I couldn't tell you who did the study that came up with these figures or when it was done.

    As far as what blue can do to traffic lights- I know for color deficient people, it usually helps. Not sure how the general public reacts though.
    Have I told you today how much I hate poly?

  3. #3
    OptiBoard Professional Michael I. Davis's Avatar
    Join Date
    Apr 2010
    You might want to check out a UK OD/DO site.

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