Camera Comparo: iPhone 4S and Canon 5D Mk II

The major advantage the Canon has, is that it is a full frame sensor. So, if you want the shallow depth of field look, then that's the way to go. The iPhone has built in image stabilization (which I think depends on the lens for the Canon) and it does it in a really great way. Rather than cropping the image like the old digital IS methods, it adjusts what part of the sensor it takes the 2megapixel video image from, based on the built in gyroscope and accelerometer.

The 8MP sensor in the iPhone 4S apparently delivers the full 8MP image at 30 frames a second, letting the the CPU or GPU convert it to an HD frame.

In traditional cameras, they have to build into the sensor the ability to take a subset of the sensor data, because they cannot read off the full sensor that fast. In the 5D mk II, they actually just skip lines of resolution to get their HD frames, which results in some bad artifacts for certain scenes.