James Holland wrote:
> [...] Looking at the catalogues I can get various
> wavelengths and the highest light output appears to be from those
> with a more yellow output, around four times that of a pure green
> LED.

The method used to specify light output will favour light sources with
a wider spectrum.  So the light output specification is best used when
comparing devices of a similar spectrum.

> [...] I am curious about how much of the 'extra' yellow light will
> make it through the filter which is more of a pure green colour,

I've often been wrong when judging the bandpass of an optical filter;

- my best results have been from looking at the colour made by the sun
  passing through the filter, by reflecting it onto known-good white
  paper.

- my worst results have been from looking at the filter with light
  bouncing off it, because the two sources of light (transmissive and
  reflective) combine.

> When I get the timer apart again I will post some pictures.

I've rarely been pleased with the colour in pictures, and now we would
have to worry about the colour on our viewing monitor.  ;-}

--=20
James Cameron
http://quozl.linux.org.au/
--=20
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