Fulmine Software/Mirror

 
Has the ability to freeze the on-screen image, change zoom and brightness.

Why it's better to use Mirror than the standard camera app:

 
This app will not go into sleep mode nor will it close during use.

 
Screen shines in full brightness and additional brightness correction can be easily applied.

 
You can easily control zoom level even on devices where this feature is not supported by the standard camera app!

 
You see yourself better in the dark using the light function.

 
You can quickly freeze the image without needing to take a photo and browse gallery. This function allows for a precise check of your exterior or even check your back!