|Tree Swing, Tyalgum, New South Wales|
There are five essential qualities that I value in a bag. A bag needs to be:
Big enough for all the gear for that occasion; but not much bigger. That may mean different bags for different occasions.
A "platform" big enough for changing lenses or bodies or batteries, without having to set anything down or move gear around in order to make the switch.
Comfortable enough to carry all day. It needs to be soft and have a wide, comfortable shoulder strap.
Weatherproof enough for reasonably expected conditions.
Secure enough to allow me to think about pictures. I like a cover flap that has velcro – so it's accessible, but makes a noise when I open it. And it needs a clasp for when it's time put it in the car or in the overhead locker.
I used to worry that my bags look like a camera bags, and give away the fact that I have a camera; but that's silly because I try to have the camera in my hand.
I don't think there's a perfect bag; so I'm not about to tell you what to buy. There are plenty of great bags around.