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Old Nov 4, 2009, 7:17 PM   #11
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Not dumb. You can leave the filter on, or not. The lens cap will attach to the filter the same way it attaches to the lens. There is something else to consider, however. The kit 18-55 has a wide angle of view. A conventional filter has filter mounting threads on it, just like the lens, so you can stack filters. The problem is that a lens with a wide angle of view could have some of it's view blocked by the filter and its threads. If you'll be doing a lot of shooting at wide angles (landscape, , cityscape, architectural, groups, etc.) you might want to skip the filter altogether. And while some filters are made specifically for wide angle lenses, some of them don't have their own filter mounting threads, so there's no place to mount the lens cap.

So a filter can protect the lens, but reduce image quality (especially if you don't get a good one) or you can go without to get the best image quality and hope for the best.
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well a circular polarizer, which i thought you were referring to in your original post is a rather specialized filter, mainly used in landscapes to boost saturation and give you nice blue skies. so this filter would not stay on your camera at all times as "protection". the version i linked you is a thin version, since your kit at 18mm is pretty wide. i am not sure the standard cap fits these thin versions.

if you are looking for a protective filter to keep on at all times to protect your lens. well first, i would advise against this practice unless you are in shooting environments with alot of traveling debris etc. instead protect your lens with the cap when not in use, and a lens hood while in use.

then just use the circular polarizer for your landscape days.
So I appear to be getting two different opinions here.

At this point I would invest in a better multi-coated filter, probably Hoya or B&W. Would a filter of that quality worsen image quality as TCav said? TCav also said that the filter may get in the way. Would a thin one have this problem as well, and if I simply zoomed in a little more, say 20-22mm, would I still have that problem?

And no, I am not looking to buy a filter simply for protection, I want the saturation in my photos since the majority of my shooting is done with landscapes.

Thanks.
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Old Nov 4, 2009, 8:04 PM   #12
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I'm sorry if I misled you. The multicoated filters that Hards80 are the best available. A lesser quality filter would reduce image quality. What I was talking about is the reduction in image quality due to the vignetting from the filter and its threads. And, yes, a thin filter, like the one Hards80 talked about, may help with that, but if you leave it on, you may not be able to attach the lens cap.

BTW, polarizing filters can cause their own special flavor of vignetting when mounted on wide angle lenses, and the Sony does a fair amount of vignetting at 18mm already, so you may want to rethink what you want to do. Limiting your wide angle use to 24mm might be a good idea.
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Old Nov 4, 2009, 10:59 PM   #13
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Originally Posted by TCav View Post
I'm sorry if I misled you. The multicoated filters that Hards80 are the best available. A lesser quality filter would reduce image quality. What I was talking about is the reduction in image quality due to the vignetting from the filter and its threads. And, yes, a thin filter, like the one Hards80 talked about, may help with that, but if you leave it on, you may not be able to attach the lens cap.

BTW, polarizing filters can cause their own special flavor of vignetting when mounted on wide angle lenses, and the Sony does a fair amount of vignetting at 18mm already, so you may want to rethink what you want to do. Limiting your wide angle use to 24mm might be a good idea.
Ok, thanks for clearing that up. Is there a different type of filter that has similar characteristics to a polarizing filter but with less vignetting?
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Old Nov 5, 2009, 5:51 AM   #14
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Is there a different type of filter that has similar characteristics to a polarizing filter but with less vignetting?
Yeah. Sort of. But they're more expensive. You could use one or more of Cokin's graduated filters to deepen the colors of the sky. See http://www.cokin.com/ico3-p1-6.html
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Old Nov 5, 2009, 9:27 PM   #15
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After several years of selling Minolta, Nikons, and Pentax (back when you had to focus and meter) I can't tell you how many customers came in with bent threads on a lens. So whenever I carry a camera climbing around or even walking through the zoo, I use a good skylight or UV filter. I'd rather break a filter than a lens (and have more than once.) But you should learn when to take it off for the best picture.

Polarizers do more than just give you deeper blue skies. They block light entering the lens at a certain angle helping to reduce reflections off water and windows. And if you put two polarizers on at a time and rotate them separately, you can even use them as variable neutral density filters.
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Old Nov 5, 2009, 9:31 PM   #16
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... And if you put two polarizers on at a time and rotate them separately, you can even use them as variable neutral density filters.
Does that work for Circular Polarizing Filters too? I don't think so.
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Old Nov 6, 2009, 1:13 PM   #17
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My Tiffen CPL doesn't have female threads, so I couldn't mount another filter on it. Maybe other brands are different.
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Old Nov 6, 2009, 4:55 PM   #18
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adamvk, I got this:

http://www.bhphotovideo.com/c/produc...r_Digital.html

It's a 55mm Cokin circular polarizer for $30. When I was at B&H Photo, the associate I spoke to said Cokin is also Hoya. The Cokin filter says Made in France, if that means anything.

Like TCav said, sometimes, I remove the filter when shooting wide angle (my lens is 18-70mm) because it causes vignetting.

EDIT: I just noticed the filter says "silver ring". I don't know what that means but the one I got is all black.
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Old Nov 6, 2009, 5:06 PM   #19
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Originally Posted by vvcarpio View Post
adamvk, I got this:

http://www.bhphotovideo.com/c/produc...r_Digital.html

It's a 55mm Cokin circular polarizer for $30. When I was at B&H Photo, the associate I spoke to said Cokin is also Hoya. The Cokin filter says Made in France, if that means anything.

Like TCav said, sometimes, I remove the filter when shooting wide angle (my lens is 18-70mm) because it causes vignetting.

EDIT: I just noticed the filter says "silver ring". I don't know what that means but the one I got is all black.
i would still suggest going with a coated filter. it really does make a difference on flare and reflection.
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Old Nov 6, 2009, 5:20 PM   #20
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vvcarpio

I'm not sure you want to know how that Cokin filter compares.

Lenstip did some tests recently on a number of Polarizing filters here:

http://www.lenstip.com/115.1-article...roduction.html

They later added a supplement test including some Cokin filters, since they were omitted from the first test group. Here's a Cokin filter that sounds like yours (they put it at the bottom of the list out of all filters tested, mostly because of vignetting, flare and streaking).:

http://www.lenstip.com/119.2-article...zer_72_mm.html
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