Can't help with the Sigma becasue I went with the Tokina AT-X PRO 12-24 f/4... Check out photography-on-the net, lots of good information.
http://photography-on-the.net/forum/index.php? I think I have a couple of shots posted in my archive at
http://www.checkmate.shutterchance.com
Canon Rebel 300D
Canon 70-200mm f/4L
Tamron 28-75mm f/2.8
Tokina AT-X PRO 12-24 f/4
Canon 50mm f/1.8 II
Canon 18-55mm f/3.5 - 5.6
Canon Speedlite 420EX
2006 MINI Cooper S - just for fun!
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2006 SPACE BLUE/SILVER CHECKMATE
HANKOOK VENTUS V12 EVO K110 215/45R17,MOTEGI 17X7,JCW CAI,
ALTA 15% , ALTA Tensioner, Auto-Up Circuit
CHECKMATE EYES, XM RADIO,Nuvi 360,HUGE SMILE
License Plate:MY CHKM8
WWW.TIERMINI.COM