Can I use Circular Polarizer like a UV Filter to protect the lens?

[csphua]

Hi,


I am planning to get a circular polarizer for my 18-200mm f3.5-5.6 lens. I already mounted a UV filter on it since day 1 and I never take the UV filter off. I wonder what would happen if I leave a circular polarizer filter on the lens just like how I left the UV filter on it?

I am hoping I don't need to change filter (to save the hassle) and it can be on the lens to protect it and at the same time giving me polarizing function when I need it. When I do not need polarizing function, can I just turn it off? (for example, turn to a position where it behaves the same as normal see-through glass)

[Mark Elberson]

<span style="font-size: 9pt; color: black; font-family: Verdana;"]One problem you will find is that even when it is not "polarizing" it's acting very similarly to a neutral density filter robbing you of 1-2 stops of light. For an already "slow" lens that's no good! Keep the UV on and only use the CPL when you need it.<o></o>

[Benjamin]

I can tell you straight - that is NOT the way you use a CPL filter. The CPL is meant to do what its meant to do, not to protect your lens from dust or damage. As Mark said, you will loose 1-2 stops of light and that's not good for your lens or just every lens depending on what you're doing. Take off the UV filter and put the CPL on when you need it, then switch back again.

[Dallasphotog]

Ditto Ben's advice. Your CPL will kill you in any low light situation. I forgot mine was on one night at a high school football game and spent 10 minutes trying to figure out what was wrong with my camera.

[csphua]

Thank you for all the info. I have further questions:

Can I stack the CPL in front of the UV filter? Will it affect the output if I can do so?

I am trying to find a way to not take off the UV filter when shooting outdoor to avoid exposing my lens to dust.

[Alan]

Under most conditions, you don't want to stack the filters.


If you are working in harsh environments, such as salt spray from an ocean mist, then leave it on.

[Vlad Xp]

You should not. You'll most likely end up seeing color desaturation caused by flares and other light artifacts on your image. That happens when the light enters and bounces back and forth between the multiple layers of your filters' reflective surfaces.

[Benjamin]

Can I stack the CPL in front of the UV filter? Will it affect the output if I can do so?
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Yes, physically you can as long as you are not using the super slim UV filters which does not have a screw on the outer side. And YES, that will affect your output. You will likely see vignette on your lens when shooting at 18mm or around wide angle range. Flare will likely to exist when shooting in bright sunlight (i guess that's when you use the CPL the most right?) especially when the sun is in front of you or is part of your image. Sharpness and contrast can be reduced too, depending on what kind of UV and CPL you're using. Try to get multi-coated filters, that makes a noticeable difference. But DO NOT stack filters.

I am trying to find a way to not take off the UV filter when shooting outdoor to avoid exposing my lens to dust.
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Dust is not avoidable in reali life shooting. As long as there isn't extremely too much dust, you IMAGE WILL NOT BE AFFECTED. Some dust involved when changing filter is not a problem for me, and it does not harmful your lens in any degree - blow them off afterwards if you need to, I'm too lazy to do that as long as I don't see them on my pictures. I know some people they like to keep their eqipment completely clean as just out of the box, i respect that too.

[Benjamin]

Can I stack the CPL in front of the UV filter? Will it affect the output if I can do so?
<div style="clear: both;"]</div>

Yes, physically you can as long as you are not using the super slim UV filters which does not have a screw on the outer side. And YES, that will affect your output. You will likely see vignette on your lens when shooting at 18mm or around wide angle range. Flare will likely to exist when shooting in bright sunlight (i guess that's when you use the CPL the most right?) especially when the sun is in front of you or is part of your image. Sharpness and contrast can be reduced too, depending on what kind of UV and CPL you're using. Try to get multi-coated filters, that makes a noticeable difference. But DO NOT stack filters.

I am trying to find a way to not take off the UV filter when shooting outdoor to avoid exposing my lens to dust.
<div style="clear: both;"]</div>

Dust is not avoidable in reali life shooting. As long as there isn't extremely too much dust, you IMAGE WILL NOT BE AFFECTED. Some dust involved when changing filter is not a problem for me, and it does not harmful your lens in any degree - blow them off afterwards if you need to, I'm too lazy to do that as long as I don't see them on my pictures. I know some people they like to keep their eqipment completely clean as just out of the box, i respect that too.

[Bob]

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<p class="MsoNormal" style="margin: 0in 0in 10pt;"]<span style="font-size: small;"]Most filters are obsolete with today&rsquo;s camera and software. <span style="mso-spacerun: yes;"]Filters are from the film and pre computers period when you had to modify color/effect at the point of image capture.
<p class="MsoNormal" style="margin: 0in 0in 10pt;"]<span style="font-size: small;"]When you add a filter to the optical path you increase optical distortion, flare, etc. <span style="mso-spacerun: yes;"]If you want to protect your lens from everyday hazards use a lens hood.
<p class="MsoNormal" style="margin: 0in 0in 10pt;"]<span style="font-size: small;"]When you put a filter on a wide angle lens the outer edges of the image will become softer due to the higher angle of light travel as compared to the center of the lens.<span style="mso-spacerun: yes;"] Thus, increasing the travel path of light through the glass of the filter and causing the image to be unfocused. <span style="mso-spacerun: yes;"]
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