2 leds in series with different forward voltage

[degarb]

Odd what I find. I wired one xr-c and one rebel 80 in series. At any current drive I push, the Rebel is much dimmer than at same Current drive and not being in series with the xr-c.

Now, I thought current was only factor on brightness. It shouldn't matter which led was first, or voltages. What is the explanation? (8.8 volt and variable resistor in series.)

 

[SemiMan]

One thing to consider is that the Rebel has a much wider beam pattern than the XR-C. That may make the apparent brightness of the XR-C (at least looking head on) appear to be much higher.

Semiman

 

[degarb]

I am hoping only a optical illusion, since after looking at hotspot of my xr-c with narrow smoth optic, anything beside it looks like a 5mm led, from xr-c to rebel 100.

Did another test of the two heads tonight at 400 ma current each. The two identical rebels' (one in series 8.8 volt, one off 4 AA's 5.3 volt off charger) hotspot looked similar, but I could still sware the 4 AA was at least a tad brighter. I am not easily biased.

 

[LukeA]

I don't think it's a matter of bias.