Why do cameras lose focus on certain objects? Can current technology make it so that losing focus is no longer a thing?
In: Physics
There’s a number of different methods cameras use to focus, including manual, and you haven’t specified which. The general answer for automatic focus is that the camera doesn’t know what thing in the frame you want to focus on. It has to figure out on its own what is supposed to be the object of focus and what’s in front of and behind that object. If you have one person standing far away and another closer, which one are you trying to take the picture of? The camera doesn’t know, so it tries its best to pick the one most likely.
This stems from the fact that there is a limitation on how much stuff a camera can focus on at once. This is called “depth of field”, which means the range of distance from the lens where objects will be in focus. The size of the depth of field depends on things like how long the focal length of the lens is and the size of the aperture on the camera, which is the little metal iris behind the lens. You can get a larger depth of field by making the aperture smaller, but it lets less light through, which can be a problem in low light environments.
Basically, everything on a camera is a trade-off, and even the smartest chip in the best digital camera can’t always make the same choice about what settings to use as a human might want.
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