I currently use a Think Tank Airport Acceleration, and all that will fit in it nicely.
(Replace MK III with a 5D, and that looks exactly like my Gear currently)
A Mk III will fit where the 5D is, have tested it alread.
The only issue I'd see is that its not really a trecking backpack, in that it dosn't have a fully padded wasit belt, but it does work very well for airline travel, and seems to pack a lot of kit very nicely.
As an example of how much it will carry, all of the following is sitting in that bag right now.
- Canon 5D with RRS L Bracket
- 300mm f2.8, with lens hood
- 16-35 f2.8
- 24-105 f4
- 70-200 f2.8 IS (Attached to the 5D)
- 24mm TS-E
- 1.4 Teleconverter
- 2.0 Teleconverter
- Wimberly Sidekick
- 580EX Flash
- Better Beamer
- Lee Polarizer, ND Grad, Lens hood/filter holder and adapter rings
- Drop in Polariser for the 300mm
- RRS Pano plate
- Cable Release (Timer)
- 77mm Circular Polariser
- Hotshoe Spirit Level
- Cleaning Cloths
- Spray Bottle of ZEIS lens cleaner
- Arctic-Butterfly Sensor Brush
- Canon Right angle viewfinder
- Spare Battery for 5D
- Penlight flashlight
- Magnetic Compass
- Sony portable GPS tracker.
I then attach my lightweight 213CX Induro Tripid with Acra-tech Ball head and leveling plate to the outside of the pack with the built in tripod straps. It goes on the left side, so you can still open it.
(Note: When going for a walk, some time I remove lenses just to make it lighter, and when I Fly, everything that can go into checked luggage does, just to make it lighter. I.e. Lens Hoods, Filters, brackets, etc. I fly with Lenses & Camera, and a Domke photo-vest. This has worked very well both internally in Australia, and Internationaly.
The bag comes with a removeable Laptop pouch, that slips into an elastic sleeve at the front. This way your not carryign any excess padding for the laptop if you dont' want to. Also the Backpack straps pack away behind the shoulder pads) very neatly for airlines and cars.
The only real issue I have is the belt. Its removeable which is good, but its also not a nice padded belt for walking. I wish I was able to fit the ThinkTank belt system belt to the backpack, then it would be perfect. (I've tried, and it sort-of works. Going to look into it a bit more and see if it can be done better.
Hope this helps.
Regards
Mark.