>In article <4hr29a$p1t@gail.ripco.com>, flash@ripco.com (Flash) wrote:
>> I have a Sigma 18-35 lens and wanted to purchase a polarizing filter >> for it. My only concern is will I get vignetting from the filter at >> the 18mm setting?
>> Thanks. Jordan

I would be more concerned about whether it is a good idea to use a
polarizer at all on a super-wide. Polarizers on lenses shorter than about 35mm used for horizontal images will show unacceptable
unevenness due to the change in polarization over the angle
included by the lens.
Hope This Helps