Up against traditional point-and-shoot cameras, the iPhone 4 is no slouch. Its backside illumination sensor — even at 5-megapixels — can hold its own against some of Nikon and Canon's best entry-level shooters in every day use. And as far as other smartphone cameras are concerned, Apple is in a class of its own.
Competing manufacturers would be wise to take note — and soon. Because with the iPhone 4S and its 8-megapixel sensor, Apple has managed to make its best camera even better. Here's what we know so far about how the technical improvements actually work.
The revamped iPhone 4S camera is composed of two parts: the sensor, and the lens. The sensor is an 8-megapixel backside illumination sensor with a resolution of 3264 x 2448, and boasts similar technology to what was found in the iPhone 4. In this type of configuration, an imaging sensor's photodiodes are placed on the front of the chip, instead of the back, as is typical of most other phones. This, in theory, allows more light to hit the sensor — 73 per-cent more, according to Apple — and improves low-light sensitivity.
But that extra sensitivity isn't a product of sensor improvements alone. Apple has completely revamped the iPhone 4S lens system, opening the aperture from f/2.8 to f/2.4. And while Wired's Gadget Lab claims that the iPhone 4's camera relied on four lens elements, the iPhone 4S now boasts five. In traditional camera lenses, multiple elements are used to improve image sharpness — which, in this case, is apparently 30 pre-cent sharper than the iPhone 4.
Finally, it's worth noting that Apple is now employing a "hybrid infrared filter" which is intended reduce the effects of chromatic aberration and ghosting often seen in small mobile sensors. You can already see the filter in action in one of the iPhone 4S sample images below.
With lens and sensor combined, Apple claims the results are so good that pictures can be printed "pixel for pixel" at sizes as large as 8x10. That's a bold claim, but given past experience, it's one that few other smartphones are likely to challenge.
The iPhone 4S's video capabilities have also received a welcome bump, from 720p to 1080p at 30 FPS. That effectively brings Apple up to par with most handheld Flip-style recorders. This in addition to some much-needed image-stabilization — undoubtedly digital — and a Star Trek-sounding feature called "temporal noise reduction."
Jokes aside, the latter is actually quite useful. According to this academic paper (PDF link) from Poland's Poznan University of Technology, the technique identifies motionless areas within a frame, and effectively freezes them, so that they may be filtered and processed to reduce noise. All of this occurs before compression is applied, and if the video below is any indication, might finally make mobile 1080p recording worthwhile.
And yet, some details remain unclear. For example, there is speculation as to whether Apple has actually increased the size of the backlit illumination sensor, or simply packed more pixels onto a chip the same size. The former would produce better quality images, but the latter is more likely due to space constraints. As for the revamped lens, the extra element means macro photography is now possible, but focusing distance has yet to be seen.
Next Friday, however, all will become clear.