filters do somewhat decrease the image quality. anything you put in front of the lens will affect image quality. the question is, is it noticeable.
cheap UV filters are what ppl buy usually. and while they add a measure of protection, it may cause reflections and hence affecting the image. that's why there are different brands and price range.

I assume we are talking about UV filters only. These days it might not be necessary. In the old times, films are more sensitive to UV light, which cause haziness to be seen in prints. These days, digital sensors and newer films are less sensitive to UV light, so there is no need for one unless it's a very hazy day.

So in essence, yes, it's only for protection.

This post has been edited by yoong: Nov 28 2010, 09:42 PM

You need to buy it.