I am of the belief that you should not keep a filter on your lens at all times simply to protect that lens from the bumps and bruises and scratches that can occur out there in the world. But I also understand that’s just my personal preference, and I do get the logic behind using a $150 filter to protect a $1500 lens. The key is as long as that $150 filter is really high quality. What I will never understand is the idea of protecting a new $1500 lens with a $50 filter, or a filter that is of poor quality. Why? Because if you’re going to ruin all of your photos with that cheap piece of glass on the front, why buy a great $1500 lens in the first place? Just buy a cheap lens and don’t worry about it. All of that said, DPReview recently directed me to an awesome blog post at the Lensrentals.com web site. It’s a bit tongue in cheek, and definitely over the top, but it’s actually very instructive too. Roger Cicala stacked 50 filters on the front of his camera to illustrate how horrible a photo looks with 50 filters stacked in front of the lens, but also to showcase the differences between good filters and bad. Even the good filters when stacked don’t look great. And a filter-doubter such as myself says that if five filters hurt image quality a lot, one filter is bound to hurt image quality a little. But again, that’s just personal preference—and I know that as soon as I ruin my next $1500 lens because I didn’t have a filter on the front of it, well, I just may reconsider my position.