The focus is the location where everything come together at. It is a term primarily used in wave mechanical systems like: optics, water management, and geological phenomena. glass lenses such as a...
Focus has more than one definition. It can mean the point of a mirror or lens where all light rays converge. It can simply mean a generic point of convergence, a point where everything or everyone...
If you're asking how you managed to do that, it sounds like a lens problem (smudges, dirt or defect). It can be done with a special soft focus filter, or you can modify a skylight or UV filter by...