Sometimes you use glass filters...

...on your camera, and you wonder how you ever took pictures without them. It gets messy because you can't use the same filters on all your lenses because they have a different diameter opening, but we only have 2(52 and 58 mm), so it's not so bad(yet).

We got cheap ones, to "learn" with, because, well, we didn't even really know how they worked, if they would be worth it, etc. They have been like £2-£5 each($3-$8). And that's cheap, because "quality" filters cost anywhere from $40 for a clear UV, to $100+ for a polarizer. So yeah...

This is what they look like:

They screw on to the end of your lens, the outside facing one.

So the simple ones, are the clear ones(bottom), just called UV filters. They block out UV light, which is more useful back in film days, since UV light would give your pics a bluish haze, from what I have read, so in digital days, they are used by most people "just to protect your lens". So they don't change the image(in any desirable way, but the cheap ones allegedly degrade your image slightly), they are just there in case you accidentally bump your camera lens into something, so the filter takes the scratch, not the lens. That's what we use them for.

The next one is the ND4 filter. It stands for neutral density, some call it a grey filter. It doesn't change the image either, just reduces the amount of light entering your lens. Why do you want that? So you can do this:

Without the filter, I would not have been able to isolate the rooster in the middle, and it would just be a lot of chickens...

The ducks "pop" at you, because only the ducks are in focus, this is because of the wide opening of the lens, which if it is during the day, it may not be able to do, since it will have to close up to get the right exposure because of the brightness. ND filter fixes that!

These pics were all taken with the 50mm f/1.8 lens. Which opens really wide, and gives these nice blurry backgrounds. Well, it opens wide, so it lets a lot of light in. Sometimes too much, like in bright conditions, such as anytime during the day, outside. Without the ND filter, I would not have been able to open so wide(1.8!), and the background would not have been as blurred.

Now the polarizer filter. It also reduces the amount of light that comes in, but it has a twist, since it does change the image. It is mainly for deep blue skies! It makes that blue really come out! It does this by limiting the direction in which light enters your lens, and i don't know the optics exactly, but that makes the blue sky look extra blue.

This is an example of one without the polarizer:

Notice the washed out skies... :(

And this one does have a polarizer:

Compared with this blue sky!

This is unrelated, but I love these cultural differences. Tires, spelled with a "y" here instead of an "i". I love these little differences...