Works very well: Highly recommended – Exposure-Calculator Review

As one reviewer stated, it's a bit confusing at first. And on the iPhone it seems a little daunting. But when I looked at it on the iPad the extra real estate made it come to life, and after a little practice it becomes easy to understand. My initial use was to take an iPhone photo of a dark scene that was nicely underexposed and try to replicate that exposure with a micro four thirds camera in manual mode. It actually calculated exactly what I had discovered by trial and error, only it dos it more quickly and let's me play with the settings. A superb app for what it does.
Review by bbthing68 on Exposure-Calculator.