Found out most phone cameras use 'focus averaging' and it explains so much

I was reading a photography blog last night and they said most smartphone cameras average the focus across the whole sensor instead of picking one sharp point. Explains why my pictures of my grandkids at the park always look soft even when I tap to focus on their faces. Has anyone else tried forcing their phone to use a single focus point or does that not work on these newer models?

2 comments

2 Comments

evan_anderson12d ago

You're close but it's a little more specific than that. Most phones use "contrast detection" autofocus which looks for the sharpest edges across the whole frame, but the averaging thing is more about exposure and color metering, not focus itself. If you tap on a face, the phone should lock focus there, but the problem is a lot of these newer sensors rely on "phase detection" pixels that cover the entire sensor (like a grid) and they sort of blend the distance data together to guess what's in focus. That's why faces can look soft even with a tap - the phone is still trying to be "smart" about the whole scene instead of just sticking to your single point. Some apps like Open Camera let you force a single focus area but it's hit or miss. Honestly the biggest fix is just to make sure you're not shooting in low light where the phone has to guess more.

river_adams2512d ago

It's funny you mention Open Camera because I actually tried that app last week after reading a blog post about phone camera limitations. The blog guy said most phone sensors use a "global shutter" readout that confuses the phase detection grid when there's movement. So if a person is even slightly shifting their weight, the phone blends the focus point with the background movement data. @evan_anderson is right that low light makes it worse, but I noticed even in good lighting my Pixel still softens faces if someone is talking or gesturing. The post I read said that's because the phase detection pixels are scanned row by row, not all at once, so the phone gets confused by moving edges.