Normally, I like to use sling bags that go diagonally around the torso. However, for a long and heavy lens, it is mostly necessary to get a proper backpack. I also wanted a bag that fitted the Sigma 150-600mm lens with the hood extended, ready for use, and with the camera mounted. That means the internal section needs to be almost 0.5 meters long, not leaving many choices.
But one bag which is up for this is the Think Tank Glass Limo. The inlay picture shows how the bag is supposed to be used: It can take the Canon 600mm f/4 without a camera, or the Canon 500mm f/4 with a camera mounted:
Like most Think Tank bags, it has a clever name. The name "Limo" suggests that the bag is long, and that it is used to carry high value items, which is very suitable for a high end tele lens bag.
From the factory, the bag comes with a number of velcro dividers. Also notice the collar in the background, which is used for securing the top of the lens. The blue bag to the left contains a "rain coat", for putting outside of the backpack to avoid water intrusion when it is raining.
You could use all the dividers to carry a large number of cameras and lenses, as shown below.
But why get this specialized bag just for a number of smaller lenses? After all, it is made for a long lens. And the bag does what I wanted: It does fit the Sigma 150-600mm with the hood in the ready position, and the Nikon D3300 mounted:
This way, it is a simple thing to get the camera out and start shooting.
When carrying a large and heavy lens, the bag comes with a waist band for extra support. I don't use it, and there is a room to tuck it away behind a flap on the bottom of the bag:
Here is how it wears:
On either side of the bag, there is a black stretch fabric for carrying a water bottle. It is crucial not to keep water bottles inside the bag, of course, to avoid spill on the equipment.
Also, there is a strap on either side for attaching a tripod. For this purpose, no less than four attachment straps are included:
The picture above shows a Manfrotto tripod with the Benro B1 ballhead.
The Think Tank Glass Limo is a high quality bag specifically designed to carry and protect an expensive long tele lens. I find that I can use it to carry the Sigma 150-600mm f/5-6.3 Sports with the hood and camera mounted, for easy access to quick shooting.
The bag comes with many clever and ergonomic functions. I'd be hard pressed to find any negative sides: One is perhaps that it could have been more water resistant, but then again, it does come with a rain cover.