Apple released the final piece of its iLife suite for iOS on March 7, delivering a universal version of iPhoto for iPad and iPhone (sorry, iPod touch users). We spent some quality time with the app using an iPad 2 and iPhone 4, and came away impressed with the unique user interface design, general intuitiveness, and overall power Apple managed to pack into the app.

The app has a lot more photo tweaking capability than you might expect from first blush, including fully non-destructive editing that can be selectively undone. It also improves a bit on the standard Photos app's organization, and greatly enhances sharing options. More importantly, for $4.99 you get a photo editing tool that can, in many ways, out-Photoshop Adobe's own Photoshop Touch.

As we mentioned, iPhoto is a universal app, so you can use it on iPads as well as iPhones. Apple says it's compatible with iPhone 4, iPhone 4S, and iPad 2 or higher, and requires iOS 5.1. We verified with Apple that as far as functionality is concerned, the iPad and iPhone versions are identical.

The iPhone version has some UI differences, which we'll discuss later, but it's worth noting that the iPhone version lacks one feature which we think is really important: tool tips. Turning on these tool tips can really help you take advantage of all the options iPhoto can offer, and we suspect that some users will get tripped up—like we did—without them. iPhoto has some really interesting thinking when it comes to its user interface that becomes intuitive after some use, but it can be confusing at first—especially for someone with over 20 years experience with conventional graphical user interfaces.

Get your iPhoto on

When you first launch iPhoto, you'll be presented with what appears to be a wall with floating glass shelves on it. On the shelves will be little virtual photo albums. Each album synced from the desktop version of iPhoto will be here, as well as a special blue album that corresponds to your device's camera roll. There are also four possible "smart" albums, which give quick access to all edited, flagged, favorited, or beamed images (more on those options later). By either swiping left or right, or choosing a different tab, you also get a grid-like "photo" view, an "event" view if you sync events via iTunes, and a "journals" view, which shows the virtual scrapbooks built inside iPhoto for iOS.

Note that events and journals also appear on floating glass shelves. Like many of Apple's recent apps, iPhoto for iOS relies heavily on "skeuomorphism," or making UI elements that look like their real-life counterparts. For instance, journals look like little Moleskine notebooks. In some cases the ornamentation is superfluous, in other cases it limits or impedes functionality (see Lion's address book). We won't make an aesthetic judgement, but in our experience, Apple's use of skeuomorphism works well in iPhoto.

These views let you look through your images as well as pick one for editing. Choosing an image loads it into a larger view, ready to apply the various editing tools. Tapping the "grid" icon on the top toolbar will show images in a scrollable thumbnail view, either to the left of the selected image (iPad) or along the bottom (iPhone). On the iPad, you can adjust the width of the thumbnail column to show one, two, or three columns of thumbnails at a time. The iPad also offers an additional drop-down menu that lets you limit the displayed thumbnails to just flagged, edited, or "hidden" images.

The basic tools are, from left to right, auto-enhance, orientation, flag, favorite, and hide. (The iPhone doesn't have the orientation control, however.) Auto-enhance does the same "magic" that it does in iPhoto on the desktop, and the results are generally good for the average photo. Like most automatic tools, however, don't expect miracles. You can rotate images 90 degrees with the orientation tool, clockwise by default or counterclockwise by holding on the icon to bring up a contextual pop-over. Tapping the flag icon "flags" a photo (as you might flag certain e-mails for later actions), tapping favorite marks an image as a "favorite," and tapping the "X" hides an image. Hiding an image does not delete it; it merely hides it from view.

Flagging and favoriting images is useful for various sorting and sharing options. Flagging is best thought of as useful for making a temporary selection, such as flagging all your images from the beach that have surfers in them. You can used the flagged status to later create a journal, or send a group of images to Facebook or Flickr. Favoriting is more or less a simplification of iPhotos five star rating system, where images are either zero stars or five stars. iPhoto also lets you filter images that are favorite for sharing options. Flagging, favoriting, and editing images add small icons to image thumbnails to show their status at a glance.

One interesting feature when selecting images is that you can double-tap a thumbnail to have iPhoto automatically select "similar" images. The selection algorithm looks forward and backward 20 images from the selected image and looks for color, contrast, and luminance similarities. According to Apple, it doesn't use image recognition technology, so it can't tell if you're looking for pictures of "boats" or of "grandma."