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Susan Jane Allen
BetterPhoto Member Since: 8/20/2005
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Circular PL and wide angle


I have two related questions, but find if I have more than one question, it's better to do it in separate threads. So, here's the first one:

A friend, here in Japan, just purchased the 18-200 Sigma lens for me online--(shipping cheaper with Japanese retailers). I wanted him to buy a Hoya UV and circular polaizer at the same time, but the price that site was asking was incredibly high ($130some for the PL), and worse, it was a Kenko (which I've had bad performance from) so I just had him get the lens.

But, curious as to how a circular PL filter could be so high, I did a bit of internet research and found that there are Circular PL filters that are super thin and this is because some vignetting occurs with "very" wide angle lenses and this compensates for that. I also noticed that the super thin ones are about $139, so my friend's dealer must have been offering that.

My question is: How much difference in performance would this super thin filter make for me, with my 18-200 Sigma? Is this lens considered "very" wide? I bought it because opportunities for landscape photography are great here, and I also like to be able to switch to macro or closeup without having to switch lenses or carry them.

My next question concerns what exactly wide angle means and how to identify it with the numbers. I'll do another thread!


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8/30/2006 9:00:55 PM

 
Bob Fately   Susan, the only performance difference would be vignetting with a wide ehough angle of view - the thin PL filter is the same piece of glass mounted in a brass ring that does not have any threads in front (at least that's how it is on my B+W filters).

As for whether you need one on that 18MM focal length - I presume you're talking about a DSLR camera, so it really depends on the "crop factor" involved.

In traditional 35MM film cameras, lenses shorter than 21MM were/are considered "ultra-wide" and generally benefit from a slim polarizer. But with a crop factor of, say 1.5, that 18MM length becomes the equivalent (more or less) of a 27MM on film, that is, not wide enough to require a slim filter mount.


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9/1/2006 6:41:11 AM

 
Susan Jane Allen
BetterPhoto Member Since: 8/20/2005
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  Thanks for answering Bob! If I understand correctly, then it wouldn't make enough difference on my Rebel XT with the 18-200 lens to go out for the ultra thin?


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9/1/2006 7:34:52 AM

 
Bob Fately   Yes, Susan, I think that is correct. The regular PL should be okay to use.


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9/2/2006 7:25:55 AM

 
Susan Jane Allen
BetterPhoto Member Since: 8/20/2005
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  Thanks!


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9/2/2006 8:53:31 AM

 
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