Wesley's Tool-Box

One of the things I've noticed about the iPhone's camera is that its field of view seemed to change with each generation, especially in the early days. This meant that the focal length was different. While the EXIF data does show the 35mm equivalent focal length, I wondered if this was really accurate. I wanted to check this out before doing deeper comparison.


By taking photos of a tape measure from a set distance and calculating the focal length with a formula, this is what I got. The last three generations have been stable - they all report 29mm, and the actual measurements are nearly the same at around 30mm. For the three generations before that, the measured values are around 32 to 33mm, although the reported values exceed this by a mm or two.

Interestingly, 3GS has the longest focal length of all at about 37mm. It isn't particularly good for selfies or group photos, and since it didn't have a front-facing camera, this was doubly unfortunate. As the selfies and wide-angle lenses became popular, perhaps Apple saw this as a problem and kept reducing the focal length until iPhone 5S in addition to adding the front-facing camera.


Now I decided to figure out the optical resolutions of the iPhone cameras. This is done by using the ISO 12233:2000 chart and looking at the test lines to see how far each of the lines remain distinguishable. I've done this test five years ago with 3GS, and I had promised to revisit it with newer iPhones. It's rather long overdue, but it's definitely worth it.

Considering the processing done to the output photos, conventional sensors would be alright with Lines per Picture Height (LPH) being 65% or greater of the sensor resolution. Let's see how the iPhones have progressed throughout the years. The photos were taken in a sufficiently well-lit room so that the lowest ISO setting would automatically be chosen by the default camera app.


Sharpening applied to the image processing during the iPhone 4 to 5 eras have apparently enhanced the percentage slightly, while the more recent ones have toned this down and still maintained the numbers in the high 60s. So it seems that the optical resolution has been kept up with the increase in the sensor's pixel count more or less. It does seem that, to go beyond 12 megapixels used in 6S Plus, Apple may need to opt for a sensor size increase to avoid degradation in quality.

When you upgrade to the latest high-end device, you would expect it to perform faster than the last one. Thanks to the ever-progressing technology this has always been the case with the flagship iPhones, but the performance jump was not always consistent. Let's see how the seven generations of the iPhones stack up.

One thing to note is that I'm probably not missing much by not having the original iPhone or iPhone 3G here. Many of the tests are already flaky with iPhone 3GS or 4, largely due to not getting a newer OS. 3GS at least is barely holding on with an OS that got its last security patch in February 2014. iPhone 3G is considerably worse, with its last update in November 2010, nearly five years ago.

First up is the GeekBench 3, as shown in the video. 3GS was able to run the 3.1.1 version of the benchmark on iOS 6.1.6, while the 4 ran the 3.2.0 version on iOS 7.1.2. All the others were running the latest version at the time of the writing, 3.4.0, which supports iOS 9.0.2 installed on the devices.


Links to Results
[iPhone 3GS iPhone 4 iPhone 4S iPhone 5 iPhone 5S iPhone 6+ iPhone 6S+]

The results provide some interesting observations. There are two instances where the performance upgrade wasn't quite as significant as the other times: 3GS to 4, and 5S to 6 Plus. These were the times when the screen resolutions saw a significant jump from the predecessor - 360x480 to 640x960 and 640x1136 to 1242x2208 (downscaled to 1080x1920 on the display), respectively, which is about 4 times the pixel count. Much of the enhancements seemed to have sunk into supporting the higher display resolution.

In the other times, the performance increases approximately twofold each generation. At the transition from 4 to 4S, this was achieved purely by going dual-core. Since then the per-core performance was boosted. In the end, you can see an 11-fold improvement for going from the first dual-core iPhone (4S) to the latest (6S Plus).