There is a seemingly endless number of photo-processing apps for the iPad, but rarely does one combine the words "powerful" and "free" as iDarkroom HD does. It allows you to layer effects onto a photo, adjust the intensity of the effects, and then share or save your edited masterpiece.
After launching the app, you can either take a photo or select one from your photo library or Photo Stream. Both buttons for these actions are located in the top row of menu options, along with settings, sharing options, a revert button to undo any changes you've made to the current photo, and a dice button. The dice are for when you are feeling lucky and want to apply a random selection of effects with a single tap.
In settings you can choose to save the original photo, which creates a duplicate for your edits. You can also select from five resolution settings, including full resolution. And you can log out of Twitter, Facebook, Flickr, Tumblr, and Evernote, but to enable any of these sharing services, you must do so in the sharing menu. When I tried to connect to my Facebook and Twitter accounts, I encountered a bug that prevented a successful connection to either.
Sharing issues aside, the editing tools that iDarkroom HD provides are fun and powerful. The tools are located in two places. Along the bottom of the screen is a row of six buttons. From left, they are: color filter (cross process, vivid, B&W, etc.), paper (for adding texture), noise (old movie, peeling, scratched, and the like), light leak and bokeh effects, vignette, and borders. Between the photo you are editing and the bottom row of menu options is a slider, which you can use to adjust the intensity of the effects.
Tap on the dropper icon next to this slider and you can access three more editing tools: cropping and rotating, blur, and a third that lets you adjust levels for saturation, contrast, brightness, gamma, and color temperature.
I hope the bug with sharing gets fixed soon, because iDarkroom HD is a great app for tweaking the look of your photos. With the number of tools it provides along with the slider you can use to adjust the intensity of each effect, you can create wholly unique photos. Plus, you can't beat the price, at least while it lasts; the app is free for "a limited time only."