The iSight camera on the iPhone 6s and 6s Plus sports 12MP
The older iPhone 6 and 6 Plus have also been capturing crisp photos even in low light, and the raw images of the new iPhone 6s and 6s Plus do an even better job in low light. Even in mixed lighting conditions the camera has an incredible exposure range. For example, if you take a photo of a person next to a window with lots of natural light in a room that is filled with artificial lights (e.g. ceiling lights, lamps.) Artificial light tends to produce a slight red tinge while natural light can have a slight blue tinge in the photo or video. Mixing the two is usually not a good idea. But the new 12MP iSight camera does a really nice job of color balancing.
Finally, the new iPhone 6s and 6s Plus can shoot not only in HD but in 4K. On a much larger screen 4K video will have a much more detailed and smoother picture. Will you be able to tell the difference on an iPhone? No you won’t. If you plan to edit the iPhone 4K video footage on your computer, you would be able to scale and zoom the footage significantly without loosing any resolution which can be very helpful when the final video is shown in 1080 HD on a TV sized monitor or large desktop monitor. Most current playback methods (YouTube, most TVs, tablets, smartphones) will see no difference in the resolution and clarity when comparing 1080 vs 4K. 4K video will no doubt play a role in the future for consumers and filmmakers. But if you plan to shoot your next documentary on an iPhone for the big screen then the 4K capability will be an excellent upgrade – just make sure you have plenty of memory and disk space on your iPhone 🙂
If you are planning on upgrading from the iPhone 6 to the iPhone 6s – I would say it is not a significant leap forward by any means. However, if you are upgrading from an iPhone 5s or older you will be fascinated with the improved video and photo quality.