Not so many years ago, when photographers needed to adjust a photo, they'd have to spend time in the darkroom tinkering with equipment and chemicals. Then along came digital imagery and the magic of Photoshop, which brought photo manipulation out of the dark. Nowadays, smartphone apps can manipulate photos in myriad ways.
The granddaddy of photo manipulation on a smartphone is Photoshop. The Photoshop Touch app is a touch-screen version of the original ($10 for a tablet version on iOS and Android, $6 for iOS and Android phones). It's powerful and can apply many of the effects you have seen in magazines and on the Web. That includes adjustments like the tilt-shift effect, which can make a townscape look like a miniature model, as well as better-known effects like red-eye reduction.
A tutorial shows beginners how to manipulate sample photos, step by step. Soon you'll be experimenting on your own.
Because of its complexity, however, this app isn't ideal for occasional use or for simple touch-ups of your holiday snaps. Unless you take the time to make yourself familiar with it, you'll easily get lost in its hundreds of settings. You may find it hard to remember the purpose of its many icons.
A simpler app, Photoshop Express (free on iOS and Android) is ideal for quick fixes because it has only about a dozen effects. It's great for cropping or quick brightness adjustments. It has clear controls and an obvious mechanism for undoing changes, though it would be nice to be able to undo an earlier effect without changing later adjustments.
You can also use it to share your tweaked photos via e-mail or over social networks like Twitter. It's a simple app, and there's little to dislike about it.
For a different, more entertaining experience, Snapseed is free on iOS and Android. It doesn't have Photoshop Touch's range of functions, but Snapseed's tools are presented in an interesting, gesture-based interface.
Icons represent different adjustments it can make, including cropping, rotating, tilt-shift effects and retro-looking filters.
After you choose a photo from your phone's library and select one of these effects, the app takes you to an editing page. You'll see the image you're working on and a simple icon bar at the bottom. In many cases, you adjust the selected photo effect with screen gestures: to crop an image you simply drag a finger from any corner of the image until you achieve the framing you desire.
Other settings, like rotating the cropping window, are controlled via the icon bar. You can hold your finger on the Preview button to see the photo before and after you've applied your chosen effect. When you're satisfied, click Apply.
Some of the effects are beautiful. But I'll admit that, even though this is one of my favorite apps and I'm practiced in its use, I find it easy to forget which gestures do what. Fortunately, the app reminds you when you start work.
A great alternative $1 app on iOS is Luminance. A full-featured app, it's a little like Photoshop Express, but with a few more effects and a slightly different interface. It's much more icon-driven than Snapseed and is a little more intuitive than Adobe's apps.
For example, clicking on the icon that looks like a group of slider controls brings up a panel where you can adjust features like brightness, contrast or color saturation by moving a slider. The app also has a timeline of your edits so that you can see exactly what you did to your photo in the order you did it. It doesn't have much in the way of tutorials or instructions, though, so mastering it may take some trial and error.
Google has given the free YouTube app for Windows Phone 8 an overhaul, turning it into a full-featured video app. Among its features are the ability to share videos over social networks and play clips in the background.
This article originally appeared in The New York Times.