One of the biggest improvements to the iPhone 4S looks to be the camera. Apple may have added three more megapixels to the iPhone's camera, but that's just about the least interesting, and certainly the least important part of the 4S camera upgrade. The big news is threefold. Lens, sensor tech and processing hardware.
Lens
The iPhone's lens now has a maximum aperture of Æ'2.4, which not only lets in more light but also allows for a greater separation between subject and background. This shallower field of focus won't rival an SLR because depth-of-field is also a function of sensor size.
Gadget Lab, What's Inside: The iPhone 4S Camera
