One problem all of our 16-strong photo group have encountered while out shooting is intense heat. Not surprising as we are in the middle of Tanzania, but it's not so much the effect of the heat on us that's a problem (we are in coverered and shaded 4WDs most of the time), it's the intense heat haze that sets up all many of focus and clarity issues.
The shot abive was taken at 11am, way too late for most animals at Lake Manyara, but still good for flamingoes. Unfortunately the air was fiercely hot and we could not get closer than about 200m (legally, that is). Even with Canon EF100-400mm lenses and 1.4 Extenders, this was the largest we could enlarge the subject. OK but nothing heart-stopping. None of mine came out sharp - even at f16 or 22, AF or manual focus. All the others had similar problems. We weren't happy.
However after some thought and the application of a large amount of Kilimanjaro beer, we came to the conclusion the the the haze simply interfered with the camera's AF system, rendering it unable to focus. Because the haze was extreme it was also nearly impossible to manually focus as well. Even Matthew, armed with his formidable EF300mm f2.8 lens struggled. We also reckoned tripods would have helped but chose not to use them on that day.
The problem was parlttly solved by returning the next day at 7am when the haze was less intrusive. It produced significantly better results but at the end of the day, moving closer would have been our best option. Something that was not possible in a Tanzanian National Park unless special permission has been applied for and approved. Something we didn't have the time for..