Let's say you're watching your kids play in the park, and decide to take a picture.
You whip out your flagship smartphone with its excellent camera, pull up the camera app, and wait for the decisive moment to snap. But there's a problem: your kids look tiny on your screen. You have three options: get up and walk closer, zoom in, or take the picture as-is.
Which is best?
I've written before about how if your pictures aren't good enough, you aren't close enough. Your absolute best move is to get closer for the shot. But maybe you're not a camera snob: you want a nice picture to remember the day, but you don't want to trudge around finding the perfect angle to make it look gorgeous. Then you're better off not zooming in.
Camera lenses without moving parts, like smartphones, can't actually zoom in. Zooming requires changing the distances between the pieces of glass in a lens. Smartphone cameras rely on a trick called "digital zoom" — nothing more than cropping in-camera.
When you "digitally zoom" onto a subject, your phone uses only a fraction of its' sensors pixels to take the picture. It blows up the result to produce a low-resolution, compressed image emphasizing all the flaws in the lens itself. Worse, it throws out the rest of the image — context and visuals you can never recover.
Don't believe me? Here's proof:
Here's a photo I took of a caterpillar on a hike:
You'll notice the image looks pretty nice. It's sharp. The lensing is attractive. There are no obvious defects that scream "cell phone camera". The caterpillar doesn't take up the whole frame but all the pebbles give it some nice context — we don't lose anything by having it look small.
Here's what it looked like when I took another shot using digital zoom:
Suddenly all the camera's flaws stand out. Motion blur from my hand shaking, invisible in the full frame, covers a much larger swath of this shot. Lens distortions that disappear across the camera's wide-angle view look bizarre and dizzying up close. The caterpillar may look more dramatic, but the picture is now so messy that it takes a second to even figure out what it is.
The original image actually looks better when I crop it the same amount:
Not digital zooming also gives you the chance to make a nice crop after the fact. With more time to think your frame over, and more image to choose from, you can make a nice close-up image that will always look better than whatever you cropped in-camera.
Here's a digitally zoomed picture I posted on my Instagram account as a budding photographer.
It's a nice enough frame. The five figures make an attractive composition, all standing at different distances around the guy going for a lay-up. But it's hard to tell what's going on. And with most of the image cropped away in-camera there's no way to get that context back.
Here's a picture taken moments later:
The composition is actually messier here. The player on the left has lights sticking out of his neck. The four of them overlap, and the lines are less clean. But the pictures works better because I left it wide. It has its context.
When you're on your phone or any other camera with "digital zoom", don't touch it. You can always edit the picture later. But if you do it in-camera you risk mucking-up and losing context from a perfectly nice shot.
