Vibrance is an app for iOS (compatible with all devices running iOS 4.3 and later) that lets you create your own photo filters using a combination of colors, contrast, opacity and a few other tools. It's free, but for the app to be at all useful to anyone requires an upgrade to Vibrance Premium currently available for US$0.99.
When you open the app for the first time, it asks if you want to view a help tutorial. I wouldn't skip this because the UI is mediocre at best so you're better off learning the basics with a guide.
After you're finished with the tutorial, it's time to start exploring the free version of the app. At the top is the image you're currently editing, which in the free version of the app is a sample image of a woman sitting in a field. Here's the catch: unless you upgrade the app to Vibrance Premium, that's the only image available for edit. Photo import -- a basic feature in any photo editing app -- requires a paid upgrade.
Now that you've come to the realization that the free version of Vibrance is really more of a demo than a functional app, it's at least worth toying around with for a bit. Underneath the photo is an opacity slider which adjusts the transparency of the filter overlaying the photo. Slide all the way to the left and you have your original photo. All the way to the right and you have the filter applied in full effect. This comes in handy as sometimes the colors are a bit too strong.
Toward the bottom is where you create your filter. The app presents a full color wheel (or literally a color rectangle in this case) plus some preset colors to choose from, but they're so small to tap in the iPhone app that you're better off ignoring them. It's a bit easier in the iPad app which is just a scaled up version.
The gradient bar is where you add the colors you select to blend them together and create the filter. In my experience, it wasn't easy picking a combination of colors that looked decent for the photo even when I turned down the opacity. I resorted to using my favorite feature in Vibrance, the Shuffle button floating at the top right. When enabled, shake your iPhone or iPad to apply a randomly generated filter and most of them do look pretty good.
I suppose it's also worth mentioning the app includes some finer controls for saturation, contrast, brightness and hue but with the inability to import your own photos for free, these don't matter very much.
What Vibrance comes down to is this: to apply and save professional pre-made filters or create your own for your own photos, upgrading to Vibrance Premium for $0.99 is your only option. For free, Vibrance is, quite frankly, useless. That said, if you are going to spend money, you're better off with apps like Afterlight ($0.99) or Camera+ ($1.99) which have far more features for perfecting your photos and include a multitude of adjustable filters, too. Compared to these, Vibrance isn't all that vibrant.