short distance is for me up to 10 to 15m
medium distance is for me up to 30 to 50m
There was a thread in the German Nikon Forum a couple of years ago.
Some people made test shots over distance and focal lengths in comparison with other lenses.
The 200-400 is not so good with a focal length above 350 mm on distances above 50m.
I try to avoid to take pictures over long distances with a long tele lens.
The atmospheric activity just reduces the maximum resolution.
You might get just a bigger magnification of the blur.
Sometimes the weather conditions are fine and it works, but most of the time it doesn't.
During my first safaris I had the 200-400, only.
I have combined it with a D300 and a TC14 (or even TC17) to get maximum focal length for small birds.
I am not so fond to switch TCs or cameras in the field.
Therefore, I have used the same set up for larger mammals, too.
I was not 100% satisfied.
The combination of lens "features" + TC + atmospheric effects limits the image quality.
In 2010 I bought the 500/4 and I use both long lenses on Safari.
I have combined the 200-400 with a low resolution FX camera (first a D700, then the D4).
The image quality improved and I am very happy with this combination.
I travel as light as possible, to counteract mass restrictions, (i.e. no razor, no spare shoes, minimum spare clothes).
My main luggage is around 10 kg for a two week safari. The photo gear is about 20 kg.
However, it is not fun to carry the equipment around.
You need some space in the vehicle to handle three cameras and two long lenses.
Usually I travel with two friends. We share a long Land Rover or Landcruizer with three rows and a driverguide.
Preferable with roof hatches, instead of a sun roof.
Each photographer has its own row.
With three persons you can arrange to shoot in any direction.
You have a free seat for the cameras / camera bag.
You can go onto the knees to shoot from lower angular.
Benin, Eritrea, Gabon, Ghana, Ivory Coast, Kenya (2x), Madagascar, Malawi, Morocco, Namibia, Rwanda, Sudan, Tanzania (3x), Togo, Uganda, Zambia, Zimbabwe