Are you really getting all the lens you paid for?

Believe it or not – the lens you buy might not really the focal length you think it is – your 200mm lens might only be 135mm! Your 70mm lens might be 45mm! Does your lens have focus breathing? This video shows why it happens, how to test if your lens has it, and how to fix it.

Zoom lens design is the art of combining lens elements to create a lens that works in a variety of focal lengths. A zoom or telephoto lens is a full of compromises as the designers work with attempting to maximize performance across the range of focal lengths as well as dealing with issues such as weight, length, portability, easy of use, price point etc.

Basic optical theory means that the lens elements have to move closer and further from the lens to be able to focus on objects near and far. In some designs the lens actually gets long or shorter ie. you can see the movement. In other designs this movement occurs within the lens but this type of design is a compromise which robs the actually zoom abilities from the lens. So you end up with a lens is not getting the subject as close as you think it would based on the infinity rating.