Understanding Aperture in Photography with Examples

I wrote this email to a friend earlier this year when he asked why, when two people stand together in a photo but one stands further back, is one in focus and one a bit blurry. It’s a classic struggle for photographers who are taking candid photos. I thought the explanation/tutorial was useful enough to share here. I’m only the 28,878th photographer to write a blog post about understanding aperture, but I may be the first to use Dairy Queen Blizzard cups.

Photographers smarter than me have better explanations for how this works, but if you look at all four of these images you’ll see how aperture and distance work. The cups were about four inches apart (different focal planes). Imagine they are people to make this more relevant. 😁 Manually trying to change the focus on any of these only changes the spot the camera is focusing on, it can’t bring both into focus (because physics).

f/1.8
f/1.8 up close: extreme bokeh on the back cup, but even on the back rim of the first cup it’s blurry (and the text at the bottom on the front). This is “wide open” aperture that brings in the most light. ISO only 640, so a nice clean image. Shutter speed 1/30th of a second.

f/16 up close: the front cup is perfectly in focus, the back cup is mostly in focus. But the ISO had to push to 12,800 (so the image is noisy) and the shutter speed dropped to 1/6th of a second (so any movement would make for a blurry photo).

f/1.8 far away: I moved back about five feet. Look at how the blur is much less extreme; the front cup is sharp. ISO is 560 (low noise), 1/30th of a second, so no blur. The red laptop is still blurry.

f/16 far away: both cups are in focus, the laptop is in focus. ISO pushes to 12,800, shutter speed to 1/8th (so blurry photos if there’s movement).

So, basically, when taking photos of groups of people that are not lined up next to each other, you should move back, switch to a higher aperture (f/8, f/12, etc.) and hope there’s enough light to make it all work.