I briefly mentioned the belt-based camera bag system I use at my Portland Seminar. If you are thinking of ordering any of their gear, consider visiting http://thinktankphoto.com/workshop/ and entering the following code: WS-055 That will get you a free item if you spend $50 (that includes some of the pouches I list below). I absolutely love this system and find it works a zillion percent better than a backpack (you can pack the individual lens pouches into a backpack or other bag when transporting things and then transfer them to the belt when you go out to shoot. I’ve been using the system for a while and have found nothing that comes close to it. I would rather change camera brands before I’d switch to another bag system… they just did it right.
I use the Lens Changer 50s to hold three of my lenses (the 17-14mm, 24-105mm, and 100mm Macro). I prefer to use the same-sized pouch for these lenses instead of using some of the smaller ones because I can then put any lens into it instead of having to be careful to get the proper lens in the proper pouch. It’s also easier to get a lens with the lens hood into the larger pouch.
I also use the Whip It Out (my absolute favorite product) for my 100-400mm. It allows me to switch to this large lens so faster than it does to use any of my smaller lenses, so the large lens gets a lot more use than when it was stored in a backpack.
If you shoot the 100-400mm (or similar lens) using the tripod collar, then I’d also get the Lens Changer 75. The lens fits into this bag with the tripod collar attached as well as the lens hood so it’s always ready to be used.The Whip It Out fits inside the Lens Changer 75 when transporting the equipment.
I also use a All The Other Stuff bag to old my cable release, extra batteries and other stuff.
All of these bags attach to a Pro Speed Belt, which completes the system. They make all sorts of other bags, so be sure to browse their site to find what will best work for your situation.