Aperture Priority and When It's Fine to Use It
Okay. Last lesson we worked through why one fence post came out sharp and everything behind it went soft, the f-number backwards logic, aperture and depth of field, all of it. Today we're talking about a mode that lets the camera do some of that math for you.
Aperture priority is the "A" or "Av" on your mode dial, depending on your camera. You set the f-number, the camera sets the shutter speed to match. That's the whole thing.
I'll be honest with you, I have opinions about this mode, and they're mixed.
What it's actually doing
You pick the aperture because that's the thing you care about right now. Maybe you want a blurry background for a close-up shot of something in the garden, so you dial down to f/4. Maybe you want that whole fence sharp, post to post, so you go up to f/11. You set that number, and the camera looks at the light and picks a shutter speed that'll give you a decent exposure.
It's half of manual. You're controlling depth of field on purpose, which is the main thing that changes how a photo looks, and the camera's handling exposure time so you don't have to think about two dials at once while you're learning to think about one.
Where it's genuinely fine to use
Here's the thing. I spent about two years shooting almost exclusively in aperture priority and telling myself that was basically manual. It wasn't. I knew it wasn't the whole time and it nagged at me until I finally forced myself into full manual for a whole summer of hikes, just to prove I could do it without training wheels.
But that doesn't mean the mode is bad. It means I was hiding in it longer than I needed to.
Aperture priority is genuinely useful when the light isn't changing much and depth of field is the one thing you're actually thinking about. Portraits where the person's holding still. A still life on the kitchen table. Landscape shots where you want everything sharp front to back and you're not chasing fast action. In those situations the shutter speed the camera picks for you is probably close to what you'd have picked yourself anyway, so let it.
Where I'd tell you not to lean on it: anything with motion you care about. If you're shooting your kid on a bike or a dog running across the yard, aperture priority might hand you a shutter speed too slow to freeze that motion, because the camera doesn't know you care about the motion, it just knows it needs enough light. That's when you want to be back in shutter priority or full manual, choosing the shutter speed on purpose.
Practical steps to try this week
- Put your camera in A or Av mode.
- Pick something that holds still. A plant, a tool on the workbench, whatever's around.
- Shoot it three times: once at your widest aperture (smallest f-number), once around f/8, once at your smallest aperture (biggest f-number, f/16 or so).
- Look at what the camera chose for shutter speed each time. Notice it got slower as you closed the aperture down. That's the trade happening in real time, and it's the same trade you've been doing by hand in shutter priority, just from the other direction.
Check your ISO stays put while you do this. We haven't gotten to ISO yet as its own module, but for now just leave it where it is, or on its lowest number, so you're only watching two things change instead of three.
A word about not overcomplicating it
I tried to teach Tami the exposure triangle at the kitchen table once using three salt shakers, moving them around to show how the three settings trade off against each other. She listened for about two minutes and told me I was making it more complicated than it needed to be. She was right. I'd built this whole system and she just wanted to know which dial to turn.
So here's the simple version, no salt shakers. Aperture priority: you pick how much is in focus, camera picks the speed. Shutter priority: you pick how motion looks, camera picks the aperture. That's it. Everything else is detail you can pick up later.
My opinion, which I've said before and I'll keep saying: master one setting at a time. Don't try to run full manual on everything until aperture priority feels boring to you, like you already know what the camera's going to choose before it chooses it. When you get there, you're ready for the next module.
Before next time
Shoot in aperture priority for a few days on whatever you'd normally shoot on auto, and pay attention to what shutter speed the camera keeps landing on. If you start noticing it going slower than you'd like in low light, hang onto that feeling, we'll use it.