I have recently noticed that to make a shot I need to have a step back more often than I have to come up closer with my 18-55 kit lens. That gave me the reason to get a wide angle. Now at a moment a was sure to get the Sigma 10-20 f/4-5.6 for 890$ but recently found in the price lists a Tamron 10-24 f/3.5-4.5 at a price of 615$. It has a larger focal range (4mm , but still!) , is faster and cheaper! Is it really so? I don't think photographers will buy something more expensive for nothing, will they? And if I get one of these lenses, will my Cokin P-series filter holder be visible in the scene?