Beware that candela refers to luminous intensity in the peak output
direction, not to total light output. Two LEDs with the same total light
output will have different "mcd" numbers if their viewing angles are
different.

You can create a rough figure of merit by squaring the viewing angle (in
degrees) and multiplying by the peak mcd value. This is in weird units and
makes lots of assumptions but should be close to proportional to the actual
total light output (usually measured in lumens)

Sean



On Mon, Apr 6, 2015 at 12:17 AM, 99guspuppet <yes@nope9.com> wrote:

> I found some CREE LED product at Mouser.
> C503B-AAN-CY0B0251
>
> http://www.mouser.com/ProductDetail/Cree-Inc/C503B-AAN-CY0B0251/?qs=3D%2f=
ha2pyFaduikwXp24CmdxMq1GICdnzBgcXgvOzTm4AXFnV0CcevnzJNQ6PWF7qwK
>
> This is a through hole Amber LED rated at 13000 mcd at 20 ma.  ( there
> seems to be some variance in output specifications depending on where I
> look in the data sheets )
>
> I have not been able to find an equivalent part that is SMT.  Am I missin=
g
> something ?  Is there reason why SMT LED devices would be a whole differe=
nt
> world ?
>
> I am using this LED in signage ( hand-held ) that will be read in the
> range of 5-20 meters.  The sign will be pointed at cars and pedestrians.
> Would a viewing angle of 15 degrees that yields a diameter of visibility =
of
> ( 20 * .26 ) 5.2 meters at 20 meters work out well ? Or would 30 degrees =
(
> 20 * .0.5 =3D 10 meters ) be a better choice ?
>
> Gus in Denver
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