Why are some things out of focus?

Question

This applies to glasses, cameras, etc.

Why is there a focal point in the first place?

Answer 1

The focal point is your subject and anything that falls out of your range of focus (depth of Field) will be out of focus.

With glasses your distance from the lens effects what you see... They are designed to act with your own lens to create focus.
The iris of your eye acts as an aperture to control your depth of field.

Hope this helps...

Beaux

Answer 2

When you look at something, the light bounces off of the object and goes into your eyes. First it goes through the iris, which adjusts to let the right amount in, then through the lens. The lens is what makes things in or out of focus. What it does is contract or flatten out to focus the light rays so that they come together on the surface of the retina, which contains the nerve endings that sense light. Things are out of focus when the lens focuses the light in front of, or "behind" the retina. This is what makes people nearsighted and farsighted. You can see this if you take a magnifying glass and move it forward and backwards in front of one eye. As you move it closer, you'll come to a point where you can't focus anymore. That's because you've reached the limit of where your lens can contract to focus. With a camera, the only difference is that instead of a retina, you're focusing on the film plane or the imaging chip.

All lenses work this same way, weather they're on a camera, or on a pair of glasses. They focus light by bending it. Some bend outward and some bend inward. Nearsighted people focus in front of the retina so they use lenses that bend light outward (concave lenses) shaped like this, )( . Farsighted people focus behind the retina so they use convex lenses, () . Here is a link that will give you more info than you'll ever need, but they have a nice picture that shows how lenses work.
http://en.wikipedia.org/wiki/Lens_(optics)

Why is there a focal point? That's the rules God used when He made the Earth. Thank God He did or else lots of people wouldn't be able to see.

Answer 3

if i understand you right there are some things in your photo's that are out of focus? that could be because your depth of field is very shallow. your f-stop depending on what you have it set at will increase your depth of field or decrease it. your focal point is where your focus starts (what you focus on). whats in focus or not in focus behind it is your depth of field. i posted some links to lenses and optics which show you have they work.

another reason you could have out of focus spots in your photos. is that a piece of glass within your lens is out of allignment. but this would mean everyshot you take that the same area would be out of focus.
why things are out of focus with your glasses is your muscles in your eyes not working properly. being nearsighted or farsighted. or having an odd shaped cornea which is called astigmatism.

Answer 4

How an you focus on glass, at all? You can only focus something , if ever, present in / on it; such as glare, dirt, finger prints etc. It doesn't matter whether you are talking of plain glass or colored glass

Glass may appear as glass when not in focus but try to focus glass, you wouldn't see it.
Well, You can focus other's camera but not your own!

Answer 5

It focuses on the main object,or one in the middle of the viewing screen.
Everything behind that is always out of focused.