11 Dec 2016

Photography Experiment: Focus Modes Are All Unreliable At Night

I do a lot of night photography, and one major limitation I face with my camera is that autofocus doesn't work reliably at night. I have too many blurry shots. So, long ago, I stopped using autofocus at night, and started manually focusing my camera, sometimes painstakingly.

But then it struck me that cameras have different focus modes — multi, flexible spot, center [1]. Multi is the default, but would one of the others work reliably?

If you don't know how these modes work, center is what it says — it ensures that the center of the photo is in focus, and doesn't bother about the rest of the photo. Flexible spot [2] is a more flexible version of center — the camera shows a spot on the screen, a circle, and focuses on that. You can move the circle wherever you want, to focus that part. And multi is the most sophisticated, evaluating different parts of the photo to try to get it all in focus.

That's the theory. How do these work in practice? Is one of them reliable at night, so I can set it and forget it? To find out, I photographed a scene with all three modes. Multi:


And flexible spot:

Right-click each photo and open in a new tab to compare them.

As you can see, all three photos came out blurry. No focus mode worked for this scene.

But maybe this scene is an exception? Maybe, if we ignore this scene, and test others, we'll be able to reach a conclusion that one mode is more reliable than the others?

Let's try a second scene, in multi:


Flexible spot:

This time center worked, while multi and flexible spot produced blurry photos. Does that mean center is more reliable than the other two modes?

Unfortunately not. Here's another scene. This time, center fails:

while multi:

and flexible spot:

... work.

Since each mode has failed in at least two of the three scenes we've compared, the only conclusion we can reach is that no mode is reliable enough for night photography. Stick with manual focus.

[1] This is not about metering modes, which determine how bright the photo should be. This is about focus modes, which determine whether the photo is properly focused, or blurry. Or which part of the image is in focus and which part blurry.

[2] There's also a spot metering mode, but that's not flexible. It's a fixed spot at the center of the screen, at least on my NEX.

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