In article , jlloyd@apple.com says...

>I have an Elan II and need an ultra wide-angle lens mainly for
>architecture, landscape work and for QuickTime VR production. Only being a
>budding photography buff, I would like some advice.

My experience is with Nikon, and the Nikkor 15's and 20's......

>I have been trying out a Sigam 14mm which certainly has plenty of
>wide-angle. One of the drawbacks appears to be using filters with this
>lens. The instructions note that a gel filter can be cut and placed at the
>rear of the lens. Does anyone have experience with this?

This is awkward, but with much care to avoid damage to the delicate gel
filters (buy 3" ones, and cut several duplicates), it does work (I use
this system with the 15mm Nikkor, which also has no front filter).

>For a little less money I can get the Canon 20mm lens which has a standard
>filter mount and the other nice features, USM and f/2.8 compared to the
>Sigma f/3.5.

Don't worry about apertures with super-wides - you do not use them,
if you care about image quality, and super-wides can be hand-held
successfully at absurdly slow shutter speeds (I find 1/15th with the
20mm, and 1/8th with the 15mm are quite reliable), allowing smaller
apertures to be used. The 20's are more "normal" in every respect
(you will put up with many quirks to get the wider angle of the
14-15mm), but for architectural interiors, and many exteriors, a
14-15mm is darn-near essential, though so is a 20mm and a 24-28mm PC.
Given your other uses, the 20mm may make more sense, since it can be
used as a good all-around lens (Uh-HUH! Just learn how! ;-), which
the 14-15mm lenses can't be (much as I like them!).

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Hope This Helps