For combined exposure and focus, you use a single tap, and to get to the separate exposure and focus, use two fingers to tap on the screen. There's a horizon line that appears on the screen to get your photos lined up.
If you want to use Analog Camera to shap photos for Instagram, you're in luck -- the app only takes square format photos. You don't have to take new photos to apply effects or share them with your friends, as you have fast access to your camera roll and photo stream at the top of the screen while you're in camera mode. The last four photos are always in view, and a swipe down shows all of your camera roll. To visit the photo stream, you just swipe to the left.
When you grab a rectangular image to apply filters, it is immediately shown with a square crop box overlayed. You can drag the crop box around to get the right composition, zoom in if necessary and then apply the crop with a tap.
Unlike some photo apps I've reviewed previously, Analog Camera comes with only eight filters. They're all rather subtle, aiming to add a specific feel to your image without destroying it or adding a border. There's no current integration with Analog for Mac, which has been around for a while. However, the Realmac team says that a June update of the Mac app will add the eight iPhone filters.
Sharing is also quite easy. Once you've finished with a photo, you can save it to the camera roll, send it via email or post it to Twitter, Facebook or Sina Weibo. Your images can also be sent to many other apps -- on my iPhone, it gave me the choice of opening the image in PhotoForge 2, QuickOffice, iPhoto, Tumblr, Halftone, Instashare, Dropbox, Camera+, Path, Instagram and more.
If you're looking for tons of filters, you're not going to find them in Analog Camera -- at least not the current incarnation. I'd personally like to see at least eight or nine more filters added to the mix, just so I don't have to send images to another app to apply a favorite.
For a 1.0 product, though, Analog Camera for iPhone is rock-solid, easy to use and a lot of fun. Get it while it's available for just a buck.