Generally I hate the "tell me about a bag" requests....BUT...
I have just added the 100-400 (anbd am expecting a 70-200IS) to my lenses. Before, the longest I had was the 24-105. Camera is 5d w/o grip.
I prefer Domke bags, as they protect enough (for me) but are not overly padded like the Pillsbury doughboy. Unforunately, the 5D and 100-400 will not fit in the F-5X bag, which had been my favorite for "about town"...i.e. just one lens on-camera and maybe a small flash.
I would appreciate suggestions...
thanks....JOHN

. It;s a light walk with camera, one lens....maybe a flash....stretching...maybe 1 alternative small-ish lens...like a 17-40.
