How does Canon 70D adjust the lens distance?

Looking at the viewfinder (or LCD screen), you can change the viewing angle (the distance of the scene) by turning the zoom ring by hand (the force should be appropriate and uniform when turning the zoom ring). When the imaging size of the subject in the viewfinder is appropriate, press the shutter to expose.

The picture shows 18-200mm lens. You can find the zoom ring according to your lens.