How do photos taken with Android Phones compare to real cameras?

The lens and the sensor determine the technical quality of your image. The other element, you being the photographer, is the same with any camera. Phone camera sensors are tiny but then again, so are those in many lower-end point-and-shoot cameras. The popular iPhone these days uses a 1/3″, 12-megapixel sensor, while most of the premium Android phones use a 1/2.6″ sensor, usually 12 megapixels to 16 megapixels. Sony has a few models using a 1/2.3″ sensor at 20 megapixels.

Most lower-end point and shoot cameras also use a 1/2.3″ sensor similar to the one found in some of Sony’s phones. This is the popular Canon SX720 compact camera, which runs around $380. Not the cheapest you’ll encounter, not the most expensive. It’s got a 1/2.3″ sensor at 20.3 megapixels and a fairly crazy lens that runs from f/3.3-6.9 with a zoom range of 4.3-172.0mm (a 35mm equivalence of 24mm-960mm).

We are not picking specifically on Canon here. Most camera companies make a point and shoot in this class. The sort of point and shoot that doesn’t have a long zoom is kind of a vanishing breed because the fact is, smartphone cameras have had strong competition, and they’re pretty good these days. Good enough to have completely devoured the lower-end of the point and shoot camera market. So if you buy a P&S today, you’re looking for something your smartphone can’t deliver.

As you can see, this camera has a rather substantial lens even for its small sensor, and you’d expect it to perhaps deliver a better image than the tiny lens on your smartphone. And yeah, it’s 20Mpixels, whereas the sweet spot in phones this year, most of which have that smaller 1/2.6″ sensor or so, was 12 megapixels. And yes, when you need to zoom out or need a slightly wider shot, the Canon may just be better than your Galaxy S8, Google Pixel, or LG G6. Maybe.

Normal Lens vs Zoom Lens

But what about the “normal” lens shot. Most smartphones include a somewhat moderate wide-angle lens, in the 28–35mm equivalent range. But these days, they’re generally very fast lenses too, f/2.0, f/1.8, maybe even faster on a premium phone. Phones often offer a fairly decent lens design, albeit fixed, and a few phones these days offer a second camera with either a different focal length.

Another factor is the lens design. I have a couple of pro lenses for my Micro Four-thirds system: one 7–14mm f/2.8, one 12–40mm f/2.8, and one 40–150mm f/2.8. Note that the zoom range of those is modest, less than 3:1. It’s actually pretty difficult to design a really good zoom lens with a long zoom range. And the better of those, such as those used on some cinema cameras, cost big and still don’t offer the 40:1 range of this Canon.

That long zoom range is in itself a compromise. There is a chance that the image at 30mm-equivalent, whatever matches your phone’s image, will be just a bit softer than that of your smartphone. Naturally, if you’re using the zoom, you’ll get far better images than were you digitally zooming (e.g., blowing up) the phone’s image.

Shrinking Megapixels and Growing Pixels

Few years back, most Android cameras were 16 megapixels. We have that on our LG V10, and it’s the best phone camera I’ve owned. But both Samsung and Google got a better result in 2016 and this year, going to a slightly lower resolution on the same sized sensor. What’s that all about?

What that addresses is low light performance. In the bright sunlight, the 16-megapixel sensor might be a bit better, but it’s pretty close, and of course, most users are posting online, where resolution is not going to be a huge deal. But as the light goes out, the actual size of your sensor’s pixels, and the aperture of your lens, start to determine the quality of the image. A good 2016 or 2017 phone will have that fast lens and larger pixels than our Canon here. It will almost certainly produce better images in low light.

The Diffraction Limited Camera

But then again, what about the sun? As mentioned, my older 16-megapixel phone can be pretty comparable to this year’s phone with enough light.

How about our Canon here?
There’s a weird phenomenon in physics we need to consider. When you pass light through any opening — such as the lens of a camera — it bends just a bit. The narrower the opening, the more bending you’ll see. How much? If I send a perfect point of light through any old lens, I’ll get not a perfectly focused point of light, but a small disc of light called an Airy Disc after George Airy, the guy who worked out all the mathematics.

So let’s pick on Samsung for a bit. The S8 has a 1/2.55″ sensor at 12 megapixels with an f/1.7 lens. That’s 1.4 µm pixel sites, which isn’t bad for a smartphone. When I shine that perfect point of light at an S8, I get a disc of 2.24 μm in size. That’s technically the smallest feature the camera can record, and it’s absolutely larger than the pixel size. Problem?

The Airy Disc is not uniform, but a fairly sharp peak within the projected disc. So a little bit of overlap between points of light, extending a bit over the size of a pixel, that’s a problem. The Galaxy S8 has a fixed aperture at f/1.7, will not give you a problem. Where there an actual problem, what you’d get is blurring due to diffraction. Or, put another way, the limiting factor on the resolution would be your lens, not your sensor.

So, how about that Canon. In this case, we have a maximum aperture at full wide-angle of f/3.3 on that 1/2.3″ 20.3-megapixel sensor, and thus a pixel pitch of only 1.19 µm. That narrower aperture means an Airy Disc diameter of 4.48 μm, which grows to about 9.25 μm at f/6.9. This means you’re absolutely resolution limited at f/3.3 that camera will never actually deliver a true 20-megapixel resolution. And once you’re out at full zoom, you’re going to have a very, very soft image. Bottom line: the smartphone is likely to deliver a better overall image, but without the flexibility of the optical zoom.