So you are wondering about the focal length of the iPhone camera or more importantly, what is the equivalent focal length relative to a 35mm film camera?
With the iPhone 4S Apple improved the lens. The new lens has a 4.28mm focal length and f/2.4 maximum aperture. This iPhone Camera should have a better advantages in low light compared to the iPhone 3G due to the combined sensitivity of the sensor and slightly larger aperture should give the camera a one stop advantage in low light. As we noted previously, the new focal length is slightly longer than that of the iPhone 4, more akin to a 35mm than 28mm, so shots in tight spaces will be a little trickier.