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Lumens, candelas & equivalent LEDs

  1. Feb 20, 2009 #1
    I'm trying to determine the millicandela rating of an LED from a keychain to find equivalent LEDs of different colours. The keychain LED specs are as follows:

    Luminous Flux value: 4 lumens (from box)
    Viewing Angle: 30° (I got this value by comparing to LEDs with marked angles)
    Wavelength: 650nm, maybe shorter (again from comparison)
    Diameter: 5mm

    Now I used this online calculator to get the millicandela rating but it seems to take a value of ~19000 millicandelas at 30° to get ~4 lumens but it only seems as bright as one of my loose LEDs (10000 mcd, 20°, 630nm). Admittedly, I held it a little further back but when both spot sizes were equal, so was the brightness. Does this seem right?
  2. jcsd
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