# Is there a light distance chart for LED light based on the MCD rating? ?

Thanks!

Kory

I'm trying to light a desk surface from the ceiling about 6 ft above the desk. Not sure if light type makes a difference either - trying to use a natural light LED.

Thanks!

Kory

Thanks!

Kory

active| newest | oldestUsing the example quoted: 12000mcd, 25 deg and 1 metre, I reckon you only get 3.7 lux at your surface - and you probably want >>3000.

Steve

You need to know the size of the cone (

emission angleas Steve wrote). From that, you can calculate the area illuminated (= pi * angle * dist^{2), and therefrom derive the luminance (cd/m2).That last link has a nice table of "typical values," which you can use to work out how many LEDs you'll need, for example to emulate a 60W incandescent bulb. You can also use the keywords fro the discussion above to do your own search for more detailed resources.}Here is an example. The distance is 6ft. Viewing angle is 25 degrees. Mcd is 12000. Can you calculate the luminance with that info?

Thanks again!

K

And unfortunately, I didn't write the definition of luminance properly above; what I did write is quite misleading. The luminance is defined as the light output per unit area of the

source, not of the observer.If you know how big your LED is, just divide the power by the area, and make sure you take care of the units correctly (e.g. 1 m

^{2}is 1,000,000 mm^{2}).A typical LED is about 5 mm in diameter, or just under 20 mm

^{2}. Your 12 cd (12,000 mcd) example would then have a luminance of 12 cd / 20x10^{-6}m^{2}= 600,000 cd/m^{2}, compared to 120,000 for a 60W bulb.Steve