Circular polarizing filter?

Correct, basically a filter that has two parts and one of which turns and changes the polarization.

There are so many different brands and versions its kinda hard to figure out what you really need. I would just let your wallet decide, anything from B+W or any Pro Hoya should be fine. I had the normal B+W and it worked great for me, no color cast and no image degration. That one runs about $100 for the 77mm. I don't have the money for another really good one so I actually just bought a $10 one on eBay and it actually seems pretty decent but I haven't had a real chance to use it yet.

 

I had the non-slim B+W and it felt very solid, will probably get another one once I find a good deal on a used one.

 

So linear filters only work with manual focus for the DSLR and polarized circular for auto focus? I read circular will allow AF to work, but linear won't. Is this true? Some of the readings said there is more contrast allowed with circular so it can auto focus BETTER...so maybe not completely useless AF in linear. Help would be appreciated.

 

Supposedly, yes. But I have heard of linear polarizers working with autofocus on DSLRs.

I have a B&W and a Hoya filter and the B&W feels much better quality, enough so that I'd spend the extra for one next time.

 

Without a CPF:
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With a CPF:

You can see how it cuts down on glare.
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.

BTW, this is just a cheap filter because I lost my $100 CPF.
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My 58mm Hoya PL-CIR filter arrived today. I'm happy with the colors it produces, but it loses too much quality in my opinion. The images aren't sharp enough when it's at maximum polarization vs. least amount. Without the lens is the best for sharpness of course, but the color isn't as vibrant. Oh well, only $27.

 

You really do get what you pay for, I haven't really done much with my $10 CPL, but I'll be getting another B+W as soon as I have the money.

 

I've been playing around with it and it works fine...under certain circumstances.

Compare with and without filter:
With: http://img251.imageshack.us/img251/6376/img0452kv.jpg
Without: http://img411.imageshack.us/img411/4243/img0454vi.jpg

Both images are sharp when zoomed in.

Now look at this shot with the filter...not sharp at all:
http://img709.imageshack.us/img709/2681/img0460s.jpg

The ONLY difference is that the first two shots I took while sitting INDOORS behind a window. The last, unsharp, shot is when I was standing outside. I don't understand...

 

In that case it's the window, the glass used for windows isn't quite as good as in filters or lenses.

 

Not sure I understand what you're saying here. My photos with the polarized filter work best when I shoot from indoors and looking out the window. When I stand outside with the polarized filter, it looks terrible. The lighting isn't that much of a difference either. I find it hard to believe that the window is making my pictures look better as that's the main difference here.

 

Very strange, for one the sharper one was taken at f5.6 and the softer at f4. The weird thing is that the sharper one says it was taken at a focal length of 55mm while the lens is a 28mm prime.

 

The lens is a 18-55 kit lens. I used the 55mm and f/5.6 for the first two shots. 27mm and f/4.0 for the 3rd one. I did a few other pics in the front yard with and without the filter in the same settings (aperture priorty...so shutter speed differed). Still lack of sharpness. It's weird.

 

Make sure you are focusing in the correct spot, some of the softness looks like it is out of focus.

 

I love my CPF, especially with a portrait and a little fill-flash. Make the sky deep blue, the couds fluffy white. If you toss a warming filter on top, you get great results.

CPF + Fill:
http://testshootcom.deviantart.com/art/brigitte-dutch-rocks-10008180?q=1&qo=1
http://testshootcom.deviantart.com/art/Giselle-beanie-10097504?q=1&qo=1


CPF:
http://testshootcom.deviantart.com/art/Amanda-schoolgirl-29077508?q=1&qo=1
http://testshootcom.deviantart.com/art/Olivia-13-43728411?q=1&qo=1


CPF+Warming+Strobe:
http://testshootcom.deviantart.com/art/Emily-graduated-Lamborghini-41405945?q=1&qo=1
http://testshootcom.deviantart.com/art/Amand-faux-sunset-29081004?q=1&qo=1

 

So, for photographers that want to know, a circular polarizing filter is a regular (linear) polarizing filter with something called a 1/4 wave plate, which essentially re-randomizes the light as it is leaving the filter. This is needed because the exposure control in an SLR camera is done from light that is split off the incoming image by a mirror (the rest goes to your eye through the viewfinder.) Light reflects off a surface (the mirror) to varying degree based on it's polarization angle with respect to the surface angle, so the light going to the metering system varies due to the angle you have a linear polarizer set to. If large portions of your photo are strongly polarized, then at every rotational setting but one (two if you count the 180 degree opposite) it ends up sending less light than it should to the light meter resulting in an overexposed shot. The sensor itself does not care about the incoming light polarization.

Some say that linear polarizers offer better performance. This is bunk. The "circular" part is done after the linear part, which is the same in both cases. Since the sensor doesn't care what the "circular" part does, the image is the same.

If you want to buy my old linear polarizers at inflated prices because you think they are better, I'll be more than happy to sell them. (Actually, old linear polarizers are good for making variable density filters by stacking them on top of your new CP filter.)

 

I`d say it`s out of focus too. Because of the f-4 you`re going to have a shallower depth of field.

Try it again, but make doubly sure it`s focused correctly. Also try with your widest apature & smallest. See what results you get.