What is the point of infinity focus?

[oxband]

A simple question: when would I want to use infinity focus? What's its purpose?

[Cassius]

If you want to focus on a range very far from the camera you focus all the way on the far end. Far away is anything outside of the lens focal range. My 50mm ends at 10 feet. Sitting in my living room I use infinity to focus on the kitchen window. You know how your depth of field decreases at closer focusing distances? If you go out far enough the range ends in theoretical infinity. I usually only run into it doing landscape shots. On a few lenses I've noticed that infinity is actually just past what it should mean and a slight bit before infinity is good for most long range shots.

[maranfilms]

you should look for some beginner books on photography, this should help explain all the basics, just because one question leads to ten more, and these will need to be addressed before you go any further.

[oxband]

Practically speaking, I use it when i want to focus on a scene that easily over 40 feet away and i want to do it quickly before i miss anything. i just quickly go to infinity focus since i dont have time to do a more measures focus where i check carefully with my monitor. is this a bad idea for a use of the infinity focus?

[jmlau]

At only 40 feet, I think so. I believe I've filmed something over 100 feet away and still wasn't at infinity on the HMC150

[oxband]

My thinking is to do this just for a super quick adjustment when i dont have time to properly focus. I guess I could just try and get better at gauging distance. I'm not being sarcastic with that. Sometimes I think I should actually try on acquiring this skill.