What is phase shift?
Phase shift is a problem that is unique to roof prism devices. The prisms within these devices can cause a shift in light rays, leading to low contrast and poor resolution. In short, poor light focus within the binoculars results in a dim, blurry image. That said, high quality roof prism devices will use special phase coatings throughout. The coatings force light beams into phase again, making a sharp image where fine details are visible.
