I just bought the 30D, but have been debating over the choice for my main lens between the 24-70mm f/2.8L & 24-105mm f/4L IS for quite awhile (for weddings). I like the extra length in the 24-105... but want the 2.8 for low light and shallow depth of field. A guy in Samys told me that digital is not advanced enough yet to truly make a difference in depth of field between a 2.8 or 4 f- stop and the added focal length will serve me better... I've never heard this.. that the camera isn't truly reading every spot of the frame to match up with the aperture you've set?. I sure have thought I could tell the difference! What do you think of this comment.. and what lens would you choose?