Just one question, so the only reason to buy a *slim* polarizing filter is to reduce vignetting w/ wide angle lenses? By vignetting, do they mean optical vignetting or mechanical vignetting (the latter happens on some cameras)?

if it's thickness that's being reduced, it would be optical vignetting. had the circumference been reduced or widened, that would cause,or eliminate mechanical vignetting...

hmm, *thinks for a few moments*

So a slim filter reduces the distance between the two glasses, or just the thickness of the filter itself (like getting rid of the threads)?

And a...nikon filter (thats the word right?) would reduce mechanical vignetting?

One more thing: Optical vignetting causes uneven polarization or darkening the closer you get to the edges?

the way i understand it, vignetting is a peripheral issue, whereas polarization is throughout the image.... or so i believe to be the case

So if i get a normal or slim filter, the actual amount of polarization should be the same?

If i buy a filter that doesnt vignette (mechanically) then the amount of optical vignetting between a slim and normal filter should be different, but minute.?

i'm taking semi-edimicated guesses here, but i'd think the thickness would then be your only variable..to be sure, make sure one of the resident experts (which i'm not) can back me up on that

it's edumacated. ;-) Thanks for the info. I already have the filter, since it was a present from my grandma, and i dont notice any mech. vignetting. I'm not sure if it causes any optical vignetting...i'm just not sure!!! (right now your thinking, is it dark in parts of the photo?...if so it is). On some photos it does it, and on some photos it doesnt!

So new questions to anybody:

1) Does aperature have anything to do with it?
2) the same as my old question, which boils down to: is a slim any better than a normal as far as optical vignetting goes?

I have no idea what mechanical vignetting is, but the optical i can speak on. It causes the corners to go dark. On a wide angle lens if you put a normal filter on there you are going to get darkening. One other lenses it is much less of a problem (sometimes it can rear its head, but not if you have a good filter or blah blah). So moral of the story is, take a picture of a white wall with and without your filter and compare. Some lenses will do it themselves so you should do it with and without.

I'm not sure if aperture is going to do anything, but again you can try it out with the white wall.

A polarizer is going to reduce glare and reflection. Some places where it is useful is when taking pictures of water. Turn it one way and you can see through the water and see the ground. Turn it the other and you can see the sky in the water. It can also be good to darken the sky and make it prettier. It can also help bring out some colors too. Say you have the sun shining hard on a building and it reflects al ot of light back to you. The polarizer can kill some of that light and help you get the color of the building instead of the white light. Have fun playing with it. I need to get a new one now that my old one doesn't fit my new lens. They are very useful and one of the few filters that can't be replicated on the computer.

Thanks. I guess i have to see if my house has a white wall. :-S Brb...

Well, on a white wall it does vignette (optically).........i think....i'm pretty sure it does. It gets pretty dark near the corners, and my house is too dark atm to open it up to F-32 (unless i expose it fo 5 minutes) so i cant test the aperature idea. I think it wouldent matter since light still has to pass through more glass near the edges.

When i take random pics, they have very little (hardly noticable) to no vignetting that i can notice!! Yesterday however, i snapped a few and there was some vignetting, but it was fairly white outside.

I have decided i'm keeping it and saving some cash. I can always photoshop the dark areas out if i want to (which works fairly good). I still have a good many years in my life to experiment with photography, i'm only 2ish yrs into it. :-D

I can always say it was my intention to darken the edges...it's art. =P

Did you try without the filter on there? On a white one of my lenses, my 18-70 kit, i can see it, but in most shots its hardly noticeable

...oh yeah, i forgot to do that...i got caught up with the nickel and two quarters trick.

(in case ur wondering, place a nickel between two quarters, hold them horizontally, drop the lower quarter and nickel and let them drop to your other hand 1ft below...the quarter lands on top. Now catch it from 2ft, the nickel lands on top) =P

...ok i'm gonna check it now.

...just tried, and to my utter amazment, the sides are darker!!! WOOOTTT! ...who needs slim pol filters. :-D

PS: Now that this thread is wrapped up: Thanks for your help. I finally dont have to worry about this matter.