Time to be with your loved ones

Time to be with loved ones

by sat

submit your photo


Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

Take the 2-minute tour ×
Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

A friend of mine who has a lot more knowledge than me regarding photography says that I should use a polarizing filter on my lens as that will protect it from sunlight and prevent it from getting damaged by the sun.

I thought that the purpose of these filters was to prevent glare from appearing in your pictures. Do these filters actually have a dual purpose then or is my friend wrong?

share|improve this question
add comment

4 Answers

up vote 11 down vote accepted

Any filter on your lens provides some mechanical protection. Many people always use at least some filter for this reason. It's better to scratch a $30 replacable filter than a $300 lens. A UV filter is often used when you otherwise don't want a filter at all. It blocks the UV rays you can't see, but which the lens would focus differently than visible light and which the sensor or film can pick up.

A polarizing filter does not prevent damage to the sensor from direct focused sunlight. It does attenuate the sun by a little more than 1 F-stop, but that is a small amount and not much help in preventing the sensor from getting fried.

A polarizing filter also does not "prevent glare". What it does do is only let light thru that is at a particular polarization angle. When the light is randomly polarized, then it will pass only half the light in theory, which is where the 1 F-stop attenuation comes from. Of course real polarizing filters aren't perfect, so you get a little more than 1 F-stop attenuation.

A polarizing filter only matters when some light in your scene is polarized, otherwise it is just a roughly 1 F-stop neutral density filter. In nature, polarized light is usually a result of reflection off a dielectric at the right angle. Examples are reflections off the surface of water, shiny non-metal (hence dielectric) surfaces, and part of the sky light at some angles to the sun. At a specific reflection angle, all the light is polarized.

A polarizing filter can be rotated so that you can decide what polarization angle you want to pick. Depending on how you rotate the filter, you can accentuate or attenuate reflections off of water, for example.

Polarized sunglasses have polarizing filters aligned such that the polarized reflections off of horizontal surfaces (assuming you are holding your head straight) are blocked. This is useful in many situations because part of unwanted glare are reflections off of horizontal dielectrics. This is particular the case when driving. Examples of polarized reflections attenutated by such sunglasses are the reflections from the inside of your windsheild, reflections off of polished horizontal surface like your hood or the hood of other cars, and reflections off the wet road ahead of you.

share|improve this answer
    
Slightly off topic, I used to put cheap UV filters on my pro lenses back then. But with time, I noticed that they induced slight aberrations in images which were noticeable. And now I don't put a $30 glass in front of a pro-grade $3000 lens but put a lens hood instead. Protects it while not having any effect on the IQ. –  Rish Sep 4 '13 at 6:18
    
@Rish: You can't take pictures thru a lens hood, so the protection is not there when you are actually using the camera. True story: About a year ago I was taking some pictures from a bridge over a river. I took a few picture, then walked a little further along the bridge for a different vantage point. I didn't put the hood back on for the short walk, but during that time the camera managed to bounce around and the lens hit a metal object protuding from the side of the bridge. The polarizing filter got scratched and I had to replace it, but the much more expensive lens was fine. –  Olin Lathrop Sep 4 '13 at 12:20
add comment

Your friend probably meant a UV / Skylight / Haze filter. Its basic and helps cut down on haze but otherwise has little impact on the image. Many photographers use them primarily for protection.

share|improve this answer
add comment

If he said protection from the sun, then he was 100% wrong. The point of a polarizing filter is primarily to remove glare as you mentioned. It isn't needed unless the shot calls for it. It does provide some (very) basic protection to the front element, but is also just about as likely to cause damage to the lens from shards of glass scratching if it breaks. UV haze filters are also generally better for this purpose if you decide to use one since they are cheaper and impact the quality of the image less.

You don't want to use a polarizing filter unless the shot itself calls for one since it will reduce the amount of light that gets into the camera, possibly significantly depending on the shot. It also won't protect the sensor pretty much at all if you point the camera directly at the sun.

share|improve this answer
add comment

A polarizer just to " protect it from sunlight and prevent it from getting damaged by the sun " ? that feels like shame to me. Maybe your friend never liked capturing crystal blue skies , or the color of a person's eyes behind a pair of glasses.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.