Anybody had any dealings with Sigma with regard to warrantys ?
I have a Sigma 15-30mm which I thought was great ... right up till the time something inside broke 
If I point the camera above the horizontal, it's generally ok and focuses correctly - but if I then lower the camera so that it is pointing below the horizontal, the camera jerks out of focus. Then when trying to focus on the house next door, the autofocus whirrs in and says, yep fine, but the viewfinder is *way* out of focus and the camera thinks next door is less than 1 foot away!
Also, when I tilt the lens backwards and forwards, I can hear a clicking sound inside like something is moving.
I'm presuming one of the lens mountings has broken ?
Anyway, Jessops (UK) have told me that the warranty on the lens is only 12 months and as I've had the lens 15 months then I'm on my own.
Anybody dealt direct with Sigma before ? Any hints 'n' tips to persuade Sigma to fix my lens ?!
Thanks!
Cheers,
Steve.

