What is focus?

Could only be one answer: one of you needs corrective eye wear.

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...

many people suffer from vision impairment without been aware of it

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...

The origin of an earthquake underground is the focus, which is right under the epicenter which is the place above ground where an earthquake is felt.