Reading Lens is a handy utility app that turns your Windows Phone device into a magnifying glass. The visual input is provided by the phone's camera, which, by default, is magnified several times. Pinch-to-zoom, and tap to focus features make it easy to get a clear picture of exactly what you want on the screen, but there are also some useful extras including also a pause button (snapshot) and a lamp button (turn on the LED flash).

It is only fair to point out that the same thing can be achieved using the built in camera app. However, what make the Reading Lens app stand out is that the app's UI is optimised around the text magnification use case. That makes it easier to use; it's a good example of how a stand alone app, built around a particular usage scenario, can provide a superior user experience.

The most obvious use for the app is reading small text, but it will work on any object. The only limitation is how how close you can hold the phone to the object you are looking at before the camera can no longer focus. The focus distance will vary from device to device (e.g. it's between 5 and 10 cm or so for the Lumia 920).

This distance will have a direct impact on how much the app can magnify a given subject, but in most real-world cases it should be possible to achieve between a 5x and 10x magnification. 

Reading Lens is based on Reading Glasses for Windows Phone 7. The main difference between the two apps is that the Reading Lens integrates with Windows Phone 8's lenses feature, and is therefore accessible directly from the Camera app, as well as from the app list.

Windows Phone Store description:

Based on the highly rated Reading Glasses app for Windows Phone 7, Reading Lens provides a custom camera Lens to help with reading small text. This is an app you'll use over and over again. Launch it like any other app or though the camera app.

Reading Lens can be downloaded from the Windows Phone Store. The app is currently available for free, but the developers say this is a limited time offer.