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. :happy:

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:
Attachment 13611
Attachment 13612

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.

You might want to check out http://theoptom.com a UK OD/DO site.