How the pixels really work. No, really.

See, they always describe pixels as being like buckets, that collect light. That ain't it at all. They are photoelectric diodes, or a type of light controlled transistor, really. Nothing but an itsy-bitsy relay, actually.

What the heck is that you ask? A relay is a switch that takes a little tiny bit of current, like, maybe 12v battery power, and lets you switch a huge amount of current, like big floodlights or something. A transistor is a semi-conductor that does the same thing. Really just a valve. Now a pixel, being as it's a photoelectric diode, controls the voltage going through the switch, (or valve, really), depending on how much light is hitting it. Lots of light? Lots of volts going through.

If the pixel was just gathering light and making it into volts, like in the bucket analogy, you wouldn't get a lot out of it. No sensitivity, like ISO 1 or something. Using a photoelectric diode, you can pump current through it, and are only limited by the leakage. Think garden hoses here. Big valve, (pixel), gets big hose, lots of water, no leaks. Little KMart valve is gonna leak, so you're limited in what you're gonna get out of it.

Here's my dumb illustration. Kara wouldn't let me put it in the book. Whatever. (It's copyrighted, so make your own.)