The new iPhone 6S and 6S Plus come with 12-megapixel rear-facing cameras, a major improvement over the 8-megapixel cameras from recent years.
Images now pack 50% more pixels than before so you can see more details, and you also get 50% more "focus pixels" than in the previous iPhones for faster auto-focus.
Cameras with more megapixels usually sacrifice image quality in certain ways. Normally when you pack so many pixels so close together, it creates artifacts called "crosstalk": inaccurate colors and noise in your images.
Apple's team worked on new techniques to maintain image quality and size despite the extra megapixels, including a technology called deep-trench isolation, which separates photo diodes and helps to maintain accurate, precise colors.
Apple gave photographers the new iPhone 6S to capture images from around the world and show off the new photo quality. In this mountain photo, you can see a rich sky with virtually zero visible noise.
Here's another photo taken with the iPhone 6S. This was shot from a plane flying above a river delta system.
Here's another aerial view shot with the iPhone 6S. This was taken over Manhattan.
Here's another iPhone 6S photo shot in Italy. Note the salmon color at sunset that's often difficult to capture on smartphone cameras.
And here's a scarlet macaw, shot with the iPhone 6S.
Panoramas are now even more detailed in the iPhone 6S. This is a whopping 63-megapixel panorama photo — you can barely see any stitching effects at all.
These new 12-megapixel cameras are also capable of capturing 4K videos, which is a first for any iPhone.
4K videos capture a higher degree of detail: 8 million pixels in every single frame.
And you can edit those 4K videos right on your iPhone, using Apple's iMovie software.
Apple also improved its front-facing FaceTime HD camera, upgrading from 1.2 megapixels to 5 megapixels for more detailed selfies.
Now you can take flash photos with your FaceTime camera. Apple borrowed its True Tone flash technology from its iSight camera, which matches ambient light for more accurate flash lighting in your photos, by using the LED backlit Retina display to create a flash that matches the ambient light's color.
Apple achieved True Tone flash on the front-facing camera by adding a custom display chip, which drives the display to be three times brighter just for the FaceTime flash.
FaceTime flash photos works great even in poor lighting conditions.
Finally, there's a new feature called Live Photos. It answers the question: "What if you could press into your photos and they could come to life?"
To see Live Photos on the iPhone 6S, just hold onto any picture you take with the iPhone 6S or 6S Plus using 3D touch, and you’ll see a brief moment of vitality, a sense of how alive the photos are.
You can even take Live Photos with audio.
(Sorry, no audio on this one, unfortunately.)
You just take photos as you always have and the Live Photos feature automatically extends the capture moment 1.5 seconds on either side of the photos. The result is a quick series of still photos, not videos.
You can always turn Live Photos off: Just toggle the button with the three concentric circles at the top of the Camera app. This feature is on by default, but Live Photos apparently takes up twice the space as a normal photo, so take that into consideration when you're taking large batches of photos.
You can watch Live Photos on any Apple product, including on computers running OS X El Capitan. You can even set a Live Photo as your Apple Watch’s watch face so you can see the Live Photo every time you raise your arm to check the time.
Apple even created new developer APIs so third-party app makers can support Live Photos. Facebook has already committed to adding support for Live Photos later this year.
