Midweek Mobile 1

Night time is the worst time for photography if you have a tiny lens. Anticipating crowds and rain on the eve of Independence Day, I went out to get some street photos, but only took my mobile phone. It does a lot of computation to deduce the shapes and colours of what is recorded. With all that computation that goes on between the light hitting the sensor and an image being saved in memory, newer and faster computational hardware has an advantage.

But did these results actually improve over the physical limitations of the small lens? In one sense they did. If and when the sensor and imaging involve chemistry, a small lens exposes less of the chemical on the film. The result was that photos look dim. We are used to saying under-exposed for such photos. The only way to make the image brighter would then be to expose the photo for longer. But that creates a problem we call motion blur. With computation sandwiched between the sensor and image, there is a third way: the brightness can be amplified. I saw that The Family gets a much brighter image with her phone than I do, because her camera software is set to amplify more. So the problem of under exposure is replaced by that of digital noise: when you amplify, both signal and noise are usually amplified together. Motion blur can still be seen though, in the featured photo, for instance.

In another sense, the limitations of a small camera remain. A lens which is half a centimeter across cannot see details smaller than a couple of millimeters at a distance of ten meters. But this fundamental limit of resolution is reached only when the sensor collects light forever. With limited exposure the resolution drops by a factor of ten or hundred. So the image always has to balance motion blur against lens resolution. You can see this at work (at least on a large screen) in the photo above. The scene was well lit, the camera was not in motion, but the image is not awfully sharp. The computational hardware has prioritized freezing the movement of people by sacrificing the light needed for better resolution.

I suppose these photos look sharp and bright enough on phones and tablets to gather likes on instagram and tiktok. Perhaps you are in a minority if you view them on larger screens. As it turned out, it didn’t rain, so I could have taken a better camera with me. But technique is what you develop when you have limitations. A mobile phone is less obtrusive when you want to take street photos, so it is a good idea to start using it more widely for serious photography.

Phone photography changes our expectation of the interaction of camera hardware and image so dramatically that it is worth rethinking what photography means. I intend to explore this a bit in this series.