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I'm getting ready for the Smokey Mountains which I am hoping to shoot some waterfalls. Since I will not get to choose what time I shoot the waterfalls, I would like to purchase a ND filter to help compensate for what could be too much sun light. I am stumped as to which ND filter I should purchase.

At this time I have 3 lenses (ALL Canon): 18-55mm ; 50mm f/1.8 ; on the way 10-22mm

When I picked up the camera I knew nothing about SLR's and the lady told me to purchase the $20 Best Buy UV filter which I did. The 50mm has a hood with no filter. The 10-22mm will arrive Tuesday along with a Hoya multi coated UV filter.

1) Which of the 3 lens will be best for shooting waterfalls? I really don't want to constantly change filters on the UWA as it's the most expensive. But, I do not see many waterfalls so it wouldn't be often the ND is used anyhow. It's between the UWA and the kit lens for the ND filter. I'm thinking the kit lens because 58mm ring is more common than the 77mm on the UWA.

2) Which brand? I'm thinking Hoya or B & W since I would like quality & something that will last a long time.

3) What about filter density .3 ; .6 ; .9 ; 1.8, etc? .9 is said to have an f-Stop reduction of 3. Is that the same as saying if my lens has a maximum f-stop of f22 the lens will actually see f25 with a .9 density filter? .9 is said to allow 12.5% light through. If I am getting this right in comparing this number to 12.5% tint on a car, that is pretty dark!!! If I am not seeing this right, someone please explain.

I think that is it for now. Thanks for any help!

A tripod will be used with the ND filter so I am thinkin get it a little dark in which I could bring the F-stop down to bring in more light, rather then only to find out still too much light with the ND filter in use.

Body: Canon XSi

Thanks for any input!!

You've posted this question in another thread already. (See here)

My answer's posted there, and judging from your statement: "A tripod will be used with the ND filter so I am thinkin get it a little dark in which I could bring the F-stop down to bring in more light, rather then only to find out still too much light with the ND filter in use." - you don't quite understand how the ND is meant to work.

You just run a longer shutter speed rather than alter the aperture, which will in turn affect your DoF. The longer shutter speed allows moving things to be blurred.

There's also a search function for the forum - you'll find lots of information about using ND filters already posted.

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Nikonian

http://www.edtangphotography.com
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Thanks for explaining that. I don't know what I was thinking about adjusting the DOF when the shutter speed could just be altered as you stated.

Anyhow, watched a couple vids on youtube and have a better understanding of ND filters.