I have been going through datasheets of a lot of LEDs, manufactured by a plethora of manufacturers, like Vishay, Kjell, etc.

The Blue LEDs, as per my observation, have more luminous intensity than the Green LEDs that I have been going through, for the same manufacturer. That doesn't make any sense to me. Green LEDs have their spectrum of illumination in the most sensitive region of eye, that means for low radiant power, you'll get almost the same luminous intensity. However, for Blue LEDS, they certainly need to have a huge radiant intensity, because their spectrum lies in the less sensitive part of the eye, and, hence, cannot match the green LED, in its brightness. However, for e.g. Vishay has SMD LEDs with their Luminous intensity lying in the region 0.7 to 70 MilliCandela, while Green LEDs' variation is just 7.2 to 12 MilliCandelas. If I want equal Radiant intensity for Green and Blue, that won't be possible because Blue has a photopic response somewhere around 0.009 to 0.08, in general, however, Green's photopic response is 0.85-0.92

Thus, my questions are: (a) Is my analysis correct? (b) Can one have equal radiant intensity for Green and Blue LEDs?

  • \$\begingroup\$ Could be it has to do with a) different bandgaps and such leading to more efficient radiation b) blue LEDs are the basis of most white LEDs iirc, which leads to more research going into making them better. \$\endgroup\$
    – Joren Vaes
    Jun 20, 2017 at 7:55
  • \$\begingroup\$ Because they are approximately the same brightness. electronics.stackexchange.com/questions/203264/… \$\endgroup\$ Jun 20, 2017 at 8:59
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    \$\begingroup\$ candelas are already weighted by a color's luminosity function; they should compare directly. \$\endgroup\$
    – dandavis
    Jun 20, 2017 at 18:35
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    \$\begingroup\$ @dandavis I know that point. I reckon you did not notice that I wrote "Radiant Intensity" and not "Luminous Intensity" Thus, scaling up the "Luminous Intensity," according to the eye's photopic response, is what gets me the "Radiant Intensity"- which is what I need to be equal for my LEDs. \$\endgroup\$ Jun 22, 2017 at 9:07


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