There are a number of smart phone apps which use the phone's camera as a light meter. How well do these work?
The metering built into most modern cameras is very powerful and accurate, but in some cases it's nice to have a detached device. A smartphone is something I already have with me, and the app are only a few bucks, compared to $40 for a very cheap analog meter — or hundreds for a nice one.
Do these apps really work, or are they gimmicks? Can they get the same information from a scene that a real device can? Can they be used as incident-light meters without additional physical attachments like a diffuser dome? Are they accurate? How accurate, compared to the various stand-alone devices? Do the phone apps have any advantages?