The UV Filter
This is a filter that is said to block UV rays but really that only applies to film cameras as digital image sensors are nowhere near as sensitive to UV light as film is. Why I recommend them is that they add that extra bit of protection against scratches, oil from hands, and general aberrations. Think about how many times you’ve pulled out your camera and someone jerk puts the palm of their hand across you lens to block your shot. The oils from their hands can be corrosive to the coating on the glass of your expensive lens. Since I I have been in Korea, I have had to shoot a lot of school functions and this seems to be the common response to most of my students. “Oh Jason teacher has a camera!” then 37 hands try to touch the lens. A 12,000 won UV lens is a lot cheaper to replace than a 1.5 million won lens.
Circular Polarizing Filter
Now photoshop maybe a powerful tool in the digital darkroom but it simply can’t simulate the effects of a polarizer. This filter can darken blue skies, reduce glare from buildings and water, as well as increase the contrast for such things like leaves. This is a must if you are shooting landscape or cityscape shots. Think of it like putting a set of quality sunglasses on your lens.
There are a few disadvantages that you should be aware of. The first is that if you are using an ultra wide angle lens (which is great for landscape shots) you will get some vignetting that will darken the corners of the shot. The more expensive and thinner C-PL filters reduce the vignetting but they are more expensive.
Flash Parker has a great guide to filters that you simply must read.
Cambridge in Colour has two great posts about filters. The first gives an overview and the second is a more detailed look at Polarizing filters.
Hoya is one of the most respected brands of filters in the business. They are high quality but carry a decent price tag on Gmarket.
Kenko is a Japanese brand and are sold throughout Korea. A few years ago they introduced a Pro1 Digital line that provides decent quality at a reasonable price. It is more expensive than the “regular line” but it makes a difference and they have a “wide” version which I picked up when I had a lot of money they has little to no vignetting on my wide angle.