The text is a description of a camera app that gives its users the feel of the manual lens. Here is a sentence form the text:
The app is highly useful and allows all kinds of photographers to explore their creativity and offers something special to those on both sides of the viewfinder.
I am not sure about the meaning the phrase on both sides of the viewfinder.
I know the lexical meaning of the term "viewfinder". However, I am not sure about the meaning of the said phrase in the given context.