The best reason to use a smart phone to take photos instead of a camera is that you're more likely to have your smart phone with you when a photo op arises. The next best reason? Instant uploading to the Web figures high on many people's lists.

Most smart-phone photo-sharing apps let you do more than share. You can do light editing, for example, including cropping and adding fun, artsy filters to enhance your shots. You can also view continually updated "streams" of photos from friends and those you follow.

But not all photo-sharing apps are alike. I'll be going hands-on with some of the newer ones—and all are free. First, Instagram (for Android and iPhone).

Instagram is the popular mobile photo-sharing and social-network app that Facebook purchased recently for $1 billion. For now, anyway, Instagram is still a stand-alone app. It started out on the iPhone, but it recently migrated to Android devices too.

Using Instagram is simple and straightforward: You take a photo from within the app (or select one you've already taken), then apply one of the numerous retro-style filters Instagram supplies. You can try as many as you like before you commit to one, to get the artsy effect you want. You can also use the Lux feature to bump up brightness and contrast in your photo. And the Linear and Radial Tilt-Shift effects give you the ability to blur parts of your photo out.

Once you're happy with the results, you can caption and upload the photo instantly to your Instagram photo stream, which appears on your phone, and also to Twitter, Facebook, Foursquare, and Tumblr (on the iPhone, Flickr and Posterous as well). Uploading happens quickly and seamlessly.

Viewed on your phone, Instagram shows a chronological stream of photos from you and the people you follow. And a great way to find new photographers to follow is to view those your followers follow (are you following all this?). To select any photo as a favorite, you just tap the heart icon below it; you can also leave comments on photos.

Bottom line: Using Instagram is simple, it's fun, it works seamlessly—and it's free. If you've been looking for a way to jazz up your smart-phone photos, share them to your social networks, and join a savvy community of like-minded shooters, this is a good place to start.

To find out which smart phones are best for taking pictures, check our buying advice and Ratings at ConsumerReports.org.

Related:
Hands on with the new Facebook Camera photo-sharing app
Hands on with the new Flickr photo-sharing app