Originally posted by mom2mny I've noticed that a lot of people say not to use a filter. Is there ever a time that using a filter is recommended? Don't they help with the glare from water etc.?
Thanks!
Well, some filters are designed to purpose for achieving particular effects. For instance, various color filters will allow you to achieve different effects when doing B&W photography (though this can be emulated digitally now). Polarizing filters can allow you to cut through reflections on water/glass/etc. as well as deepen the color of the sky when facing in the right directions. Neutral density (ND) filters give you the ability to take long exposures even during the daytime (useful for keeping the shutter open long enough to achieve a fog-like appearance for moving water). Graduated ND filters help you to compress the dynamic range of a scene so that your camera's sensor can capture it all (the top of the filter will let less light in than the bottom half, so you would position it such that the sky has most of its light blocked, while the landscape below does not, for instance). Probably there are other effects filters of value that I don't know about, but these are the ones to come to mind.
To get more to the heart of your question, though, a lot of people say you shouldn't use filters because they degrade optical quality. Almost exclusively they are talking about UV or Skylight "filters", which do not enhance your images in any way despite dubious claims in their marketing. These are primarily marketed as
protection devices, to create a barrier between the harshness of the world and the delicate front element of your lens. The value of their use is a highly divisive topic -- it is true they can degrade optical quality because you are adding an additional piece of glass that can diffract and reflect light... Your images may appear measurably less contrasty, less sharp, and may be more prone to exhibiting flare, depending on both the lens you're using and the filter. However, except with the very worst filters, these degradations of image quality are very hard to notice, though allegedly you can notice it with some severe pixel peeping no matter how nice your filter is.
If you are looking into getting a protective filter, the question is whether you are comfortable losing 2-3% of image quality off the top (potentially). Even if you do decide to use one, you're not obligated to use it
all the time. There are plenty of places where it just makes good sense to protect the lens, even if you normally wouldn't bother -- on the beach, in high winds with particulate, around smoke or other acrid vapors, or anywhere else you might expect shit to fly through the air at your camera.