New details about the iPhone 7 Plus camera have been revealed by an enterprising Reddit user.
We now know the size of both sensors in the iPhone 7 Plus camera, thanks to some hasty maths turned out by Reddit user /u/ImKuya. After Sports Illustrated posted the very first iPhone 7 Plus images online, /u/ImKuya pulled out the EXIF data from the photos. EXIF data is coded into every image, and reveals intimate details about how and when a photograph was taken.
From that data, he worked out the size of the sensors in the iPhone 7 Plus’s dual-lens camera. It turns out that the main wide-angle camera features a 1/3-inch sensor, and the secondary telephoto camera features a smaller 1/3.6-inch sensor.
Big sensors are expensive, but improve detail, low-light photography, and depth of field, amongst other things. The iPhone 7 Plus has a smaller sensor than the Galaxy S7’s 1/2.5-inch sensor, for comparison. The main camera is the same as the 1/3-inch sensor used on the iPhone 6 and iPhone 6S, however.
So how did he work it out?
The maths explained
Firstly, you take the known quantities. Apple has already admitted that the wide-angle lens measures 28mm, and the telephoto lens measures 56mm.
Apple's iPhone 7 Plus is the first to feature a dual-camera configuration, giving it improved zoom and depth-of-field
From the EXIF data, we know that the focal length is 3.9mm. When a camera is trying to focus, the lens and the sensor move apart or closer together. The focal length is the distance between the lens and the sensor when a subject is in focus.
To find out how big a sensor is, we need to work out the crop factor of the camera. The crop factor tells us how much of a scene that a sensor can “see”. This number is almost always worked out in relation to how much a full-frame 35mm camera can “see”. That’s why it’s a ‘factor’.
To work out the crop factor, you just divide the size of the lens by the focal length of the camera. So if the iPhone 6S has a 29.92mm lens (it does) and a 4.15mm focal length (it does), we end up with a crop factor of 7.21.
(Image credit: Wikipedia) Crop factor relates to how much a sensor can see. The red box here is a full-frame sensor (24 x 36mm), compared to the blue box, which is what a smaller (15 x 23mm) sensor would see
So let’s assume that the wide-angle lens is the same on the iPhone 7 Plus. If the crop factor is also 7.21, and the focal length is 3.9mm, the product of those numbers is 28.7679, which is very close to Apple’s claimed 28mm. Success! So we can assume that the crop factor is 7.21 for the wide-angle lens.
When you know the crop factor, you know the sensor size. For instance, a 1/3-inch sensor always has a crop factor of 7.21 You can find a huge list of sensor-to-crop-factor comparisons right here, if you really care. So that means we know the iPhone 7 Plus wide-angle camera has a 1/3-inch sensor, just like the iPhone 6S.
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So what about the iPhone 7 Plus’s other sensor? Well, some of the Sports Illustrated photos were taken using the secondary telephoto lens, which EXIF data tells us features a 6.6mm focal length. Using the same method above based on a 56mm lens, we worked out a crop factor of 8.6 – that’s a 1/3.6-inch sensor.
That means the iPhone 7 Plus telephoto lens is smaller, and will perform less impressively. That’s not a surprise, as adding this second camera has been estimated to cost Apple as much as $40 more per iPhone unit.
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Watch: iPhone 7 vs iPhone 7 Plus
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