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I have some LEDS, yellow and blue. Using the exact same battery, the blue LED runs significantly brighter than the yellow one - why is that? I have tested using multiple blue and multiple yellow and blue is consistently much brighter than the yellow under the same conditions.

You can see the difference here:

enter image description here

enter image description here

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    \$\begingroup\$ Do you know the lumen or mcd ratings for the LED's you're comparing ? \$\endgroup\$
    – Nedd
    May 8, 2021 at 4:47
  • \$\begingroup\$ Different technologies. \$\endgroup\$ May 8, 2021 at 8:27
  • \$\begingroup\$ the yellow one actually looks brighter ... possibly a result of your camera and of the display I'm using \$\endgroup\$
    – jsotola
    May 8, 2021 at 14:33

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Possible reasons

  1. You seem to be powering the LEDs directly from a battery. Different LEDs have different resistance and different forward voltage drops. So, when you power directly from a battery different LEDs can draw different amount of current / power and output brightness is dependent on the input power.
  2. The efficiency with which different colour LEDs convert input power to output light is different since the materials used and construction are different.
  3. Our eye / camera sensor are sensitive to different colours at different amounts. (But blue would have had lower brightness then, I would think).
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