lincomatic:
But if you're lighting the LED's w/ a 50% duty cycle, they're on only half the time, so aren't you getting just half the brightness?
No.
Let's say you have an array of 8 LEDs, lit the traditional way. You put 10mA through each LED, and use a total of 80mA.
Now let's say you wired that same array with each pair of LEDs in series. You'd still put 10mA through each LED, but now you're using only 40mA.
So far so good.
Now let's put 20mA through each pair of LEDs in the array wired in series. You're now using a total of 80mA, just like the traditional array, but each LED sees 20mA, so they're twice as bright.
Makes sense right?
But we can't animate the array wired in series. Not if it's wired the traditional way. So we wire it using the method I outlined above. And as a consequence of that, we have to multiplex it on a 50% duty cycle, with each pair of LEDs lit half the time. That halves our brightness. But it also halves our current usage.
So you're now using a total of 40mA, and each LED sees an average of 10mA. Half the current as the traditional array. But the same brightness.
Or, to put it another way... twice the brightness of a traditional array using that same 40mA, with each LED seeing only 5mA.
Or does the nonlinearity of the eye make it appear brighter than 50%?
No, that's not what's at play here.