"N_Cook" wrote in message
...
On 27/09/2013 14:46, William Sommerwerck wrote:
Have you calculated whether you can cram enough LEDs into that space to
get the same brightness level as the discharge lamp? Or are you
expecting to learn from the test?

I'd like to point out that is no such thing as -- nor can there be -- a
white LED. LEDs are necessarily limited to a narrow band of wavelengths.
* All (???) white LEDs are (I assume) a blue LED with a
yellow-fluorescing phosphor. **

This /looks/ white to the eye, but the red and green wavelengths needed
for color reproduction aren't present.

Unless your white LEDs contain red, green, and blue LEDs, I don't think
this is going to work.

* This is actually a good thing if one is trying to match a specific
color space, and you can manufacture LEDs whose wavelengths correspond
to the three primaries.

** I'm thinking of indicator lights and such. Lamps to replace
incandescent lighting would necessarily have to put out red and green,
or colors wouldn't look right.

I've had another look at the product data and the 2 degree lenses are 4
degree , in normal terminology

I don't know what chromaticity means but for the 3500 deg K version a Cx
of about .4 and Cy of about .39
A bit more graphic the spectrum is continuous and smooth "bell curve" peak
shifted 40nm from 550nm of the standard eye response curve to 590nm
and the 50% points broader apart at 150nm compared to 100nm of the eye and
a 50% down peak at 460nm which I suppose is the potential bugbear for such
a lamp conversion


That triangular diagram that you see with red, green and blue respectively
at each corner and white in the middle, and intended to show every possible
colour that can be derived from additive mixing of those three colours, is
called a chromaticity diagram. It famously used to be used to show that a
colour CRT cannot (truly) produce brown.

Arfa