Someone also mentioned the Lowepro bag finder. It may work in some cases, but when I entered what I wanted to put in the bag, it provided choices that would not work and omitted many that would. I found the Pro Runner 350 AW by looking through their site the old-fashioned way.
Even that's a challenge, sometimes. Camera bags are one area where going into a brick-and-mortar shop is a great idea. Bring your gear, put it in the bags, see what fits and what doesn't. Try the loaded bag on for comfort.
Online descriptions can be misleading. . . .
Excellent points.
I'll just add, for example, that the shorter length of the Lowepro bag fit me much better and was therefore more comfortable on than the larger Think Tank bag. If I were taller, I might have gotten the Think Tank bag. I also forgot to mention in my earlier post that while I found this bag on the Lowepro site, I actually bought it at my local Calumet store after loading it up and trying it on.
Great points from VC and Neuro.
I bought a Dakine photo backpack online. It looked perfect for what I needed. When it arrived, it was much bigger than I had anticipated, much heavier, and rigid in a way that meant it was always big, even when empty. It had some great features and I wanted to like it, but it was kind of a beast, at least for me.
I ended up picking up a Lowepro bag at REI where I could try it on, see how much room I had after putting my camera in it (since I only had my body and a lens with me), and try out a few non-photo things in it like water bottles, etc. I'm really happy with it (Photo Hatchback 16AW) and I have sent the other bag back.
As much as I like the convenience of ordering online, trying the bag on in store was key for me.