Instead of megapixels-worth of light sensors, a

Instead of megapixels-worth of light sensors, a new experimental camera uses a series of mirrors to focus all the light on just one sensor. Somewhat related question that I’ve been wondering about for awhile: why do digital cameras need shutters? Why can’t you just turn the sensors on and off electronically? Seems like you could then use many more arbitrary “shutter” speeds, like 5 seconds or 1/50000 of a second.

• cameras
• photography