Apple pictures the future with new cameras in the iPhone 6s, 6s Plus

The biggest change is on the tin —  for the first time in a long time, Apple has bumped the pixel count in the iPhone's rear camera. After being stuck at 8 megapixels since 2011, the new 6s and 6s Plus pack 12-megapixel sensors behind an f/2.2 5-element lens.

Apple has previously justified its staying out of the megapixel madness by explaining that more pixels do not equal a better picture, and they're right. Much like the addition of the plus-sized iPhone, though, the market has spoken and forced Apple's hand.

To pack more pixels in, Apple has had to make each individual subpixel smaller and put them closer together. This often leads to slightly worse image quality as light tends to leak between subpixels, a problem known as optical crosstalk.

Apple says they've avoided potential quality loss by doing two things: shrinking the space between the photoreceptors and their color filters, and manufacturing the pixels with a process called "deep trench isolation."

While bringing the color filters closer to the photoreceptors is important —  it gives photons less room to bounce around before entering the pixels — deep trench isolation is the key to preventing optical crosstalk.

Broadly, deep trench isolation refers to a process by which tiny voids are created between pixels during sensor fabrication. Those voids are then filled with insulating material, preventing photons from moving between pixels after passing through the photoreceptors —  and making for crisper shots at higher resolutions.

Aside from making it easier to get nice crops for Instagram, the resolution bump also enables the 6s and 6s Plus to capture 4K video, a first for Apple. 4K, sometimes called "Quad HD" because it roughly represents a doubling of 1080p on each axis, is the new standard in high-definition video.

The addition of 4K capture —  and the ability to edit 4K in the iOS version of iMovie and automatically upload in 4K to YouTube —  is notable primarily because Apple has a singular ability to drive wide adoption of new technologies. Thanks to the iPhone's popularity, tens of millions more 4K-capable cameras will be in the hands of everyday consumers by the end of 2015, leading to an exponential growth in the availability of 4K content and helping to expand the still-nascent ecosystem.

Alongside the new features and redesigned silicon, two technologies introduced in the iPhone 6 series —  optical image stabilization and Focus Pixels —  have been upgraded in the 6s.

Optical image stabilization remains exclusive to the plus-sized model, but it can now be used when shooting video as well as still images. Apple has also increased the number of Focus Pixels —  or phase detection sensors, in photography parlance —  making autofocus noticeably faster.

The selfie cam hasn't been left out of the party. It received a significant resolution bump, going from 1.2 megapixels to 5 megapixels, and gained automatic face detection as well as Retina Flash.

As AppleInsider detailed last week, Retina Flash is Apple's way of describing a new technology that lets the iPhone's display function as a flash. Using a combination of specialized hardware —  a custom display driver that increases brightness by up to 3 times over normal levels —  and clever software techniques, the company has managed to approximate its well-received True Tone flash without building in additional parts.

To make Retina Flash work, the iPhone analyzes the lightning conditions using both the ambient light sensor and pixel intensity analysis of the camera's image stream. It then adjusts the brightness and color of the display to compensate, while ensuring that the flash and shutter are timed precisely together for the best results.

The excellent imaging systems have long been a differentiator for the iPhone, and Apple has doubled down on that bet with the iPhone 6s and 6s Plus.