Calculations made by the user shows that the main sensor is exactly the same as that found in the iPhone 6s, while the sensor 2x telephoto lens is somewhat smaller.
These data were taken using EXIF information of the photos from the web Sports Illustrator, where some of his photos were taken with a telephoto lens. Apple claims that the iPhone 7 has a wide angle lens 28mm (as calculated by Reddit user is 35mm) for the main sensor and a 56mm telephoto lens (35mm calculated).
The actual focal length of the main chamber is 3.99 mm, according to the EXIF data provided by one of the photos. 1/3 inch sensor has a crop factor of 7.21 to Igul the iPhone 6s sensor that is 1/3 inch.
Moreover, the iPhone 7 Plus has a telephoto sensor 56.8 mm and 1/3 inch sensor, the crop factor is 8.6.
This suggests that in the presence of a smaller for the same number of pixel sensors, this tends to mean more 'noise' in the photos, however, Apple has a good track record in reducing noise.
Now you just have to expect that the average user has photos in hand to squeeze the most of the qualities of the chambers of the iPhone7