I found the auto focus quick and accurate, and it served well except for those odd moments when trying to capture a subject such as a bird partially obscured by tree leaves, or the head of a submerged jaguar just peeping out from a bank of water hyacinth. It’s not a problem to use manual spot focus to the fix the problem, but trying to set the selector switch on the left side of the camera to Manual and then having to move my hand to the front of the lens to turn the manual focus ring sometimes took more time than I had at that moment, so the odd shot was lost.
It would be wonderful if Fuji were to figure out how to position a separate selector switch close to the manual focus ring so as to allow instant selection from manual to auto focus, and I’m sure that this may happen someday.
When using the long lens combo, I would consider the varying camera to subject distances and conditions that I would be shooting under, so would choose an f-stop that allowed me the optimum depth field for the subject chosen, and then adjust the shutter speed accordingly, using the exposure compensation button in conjunction with the rear command dial and EVF display. Despite having, on occasion, to push the ISO close to 3200 to grab the odd image of a jaguar hidden in the deep forest shade, I can discern no noise on the images.
With so many lovely birds to choose from I decided to try capturing images of them in flight. This would be opportunistic though, with my grabbing images as they took off in flight while not really set up for them, but I am happy to say that I was able to succeed to an extent by simply setting the front focus switch to ( C ) and snap shooting as the bird flew. I admit to missing a lot of images as I was continuing to use the 100-400 lens and so was not able to track as well as I wished, but again the results were adequately satisfactory.