Circular Polarizer

[UOduck23]

Are there any disadvantages to leaving my circular polarizing filter on my 24-70L 2.8 at all times?  My current setup has the polarizing filter directly attached to the lens with a clear filter (the one I bought with the lens just to protect the glass) on top of that.  I figured why not protect the polarizing filter too.  The immediate disadvantage I can think of is that it makes it impractical to take off the polarizing filter for use on my 70-200L 2.8 II.  But are there others?

Thanks in advance.

[Canon-F1]

-2 stops less light?

why not another filter to protect the protecting filter?   

honest im not strictly against protecting filters but if you use a pol filter you don´t need another filter on top of it.

[Policar]

You'll lose 1.3-2 stops of light (as mentioned above) and, depending on the angle, reduce specular highlights.  This can be nice (foliage at noon) or it can ruin skin tones in portraits.  Shooting LCD screens won't work, either.

[wickidwombat]

and you cant stitch panoramas properly that are shot with polarisers on it makes the sky go all crazy

[dmills]

To put it another way, your nice 24-70 f2.8 and 70-200 2.8 ii becomes an f5.6ish in terms of attainable shutter speed

[JR]

I agree the loss of 1-2 stops can be costly in shutter speed or ISO performance in some situation.  Originally I had started to shoot with circular polarizing filter whenever I shoot outside in the sun.  I since then dialed back on their use to only use them in some situation, mostly for landscape or when I dont need to "freeze" the action.

With the polarizing filter on, I missed several shots where I needed to a higher shutter speed...They are a good tool, but I would not recommend them on all the time.

[scrappydog]

... if you use a pol filter you don´t need another filter on top of it.

This was my thought.  I would put the clear filter on the lens for protection and only attach the polarizer when you need it.  A polarizer is helpful in lessening glare, enhancing shadows in flat light, and boosting color saturation.   As noted, the polarizer will block some light so it's best used only as needed.

[D.Sim]

personally the only use for a clear filter would be front element protection... Mostly because that said front element is neither cheap nor easy to replace. A CPL isn't that cheap, sure, but its not gonna cost a bomb to replace either. The image degradation from the additional filter just isn't worth it... and if you really wanted to protect the filter, take it off when its not needed?

Personally I only ever take out the CPL when I want to reduce reflections... or use the lights in the sky. Even then... not always.

Its just not worth it staying on the glass long term.

[UOduck23]

I love the CR forum.  You guys completely answered my question.  Thanks.