Sorry for not making myself clear — those pics were taken using a Panasonic 100-300, and I included them because I felt that that lens was not getting enough credit in this thread. In my experience, its IQ is every bit as good as that of the 100-400, though it's very possible that I got lucky with a particularly good copy of the former and a bad copy of the latter. And as you know, the 100-300 is a bit faster at the long end than is the 75-300.
It's an unfortunate aspect of nature's sense of humour that most visually interesting wildlife action typically takes place at dawn and dusk. Once the sun is fully up, the higher predators of the African plains generally devote themselves to sleep. Most of the hunting action happens at either the beginning or end of the day, when light levels are comparatively low. Kenya is on the equator, and consequently dawn and dusk happen very quickly — one moment it's dark and thirty minutes later you're looking for your hat, so in practice the difference between f/5.6 and f/6.7 probably only represents about ten minutes of the day in terms of available shooting time, given an arbitrary set of acceptable shooting settings (maximum ISO and minimum shutter speed), but... they're likely to be ten quite valuable minutes.
But it's important to maintain some kind of perspective — I'm confident that you are going to have an amazing experience in Kenya, regardless of the contents of your camera bag and ultimately that's what matters most, in my opinion. It's a humbling and inspirational thing that goes far beyond any photographic activities. Even if your main aim is simply to relax in amazing surroundings and you choose to sleep in and just amble about at leisure later in the day, you'll be able to capture some memorable images with practically
any camera gear — certainly with any of the stuff currently under discussion. On the other hand, if the photographic aspect is more of big deal for you, my advice is to take the fastest lenses you can afford. In this regard, my opinion respectfully differs from
@oldracer 's — when it comes to photographing wildlife there is no substitute for a fast lens — at least, not if your aim is to maximize the available opportunities. i have to admit that to some extent I view it as a challenge from the animals themselves, albeit a somewhat humorous one: if they think they can outwit me by doing the things I want to photograph at times where there is little light, I'm going to my darndest to overcome that hurdle!
Of course, it's a foregone conclusion — they're going to win the challenge every time — but it's fun to try nevertheless. Dawn is when the hippos are returning to the rivers from their nocturnal grazing grounds, when the mist is rising from the water as elephants make their morning commute to the river from the relative safety of the hills, when cats are slinking through the bluish light in search of a meal — there's nothing like it, but it
is challenging. I could post a series of images, shot over the space of a couple of hours, while waiting for a leopard to wake up from its lair beneath a tree, high up on a rocky ridge. They start with the 100-300 (leopard sleeping on its back in long grass, only feet visible), progress through the 40-150 Pro (wakes up, moves down the ridge by stages, running from cover to cover) and end up with the 75/1.8 (finally emerges quite close to us — great opportunity for a moody shot). Unfortunately, by that time, it was practically dark (1/15 second, f/1.8, ISO3200) and she was
just too far away for the photo to be a real keeper. Which is why, on my next trip, I'll be taking the Oly 150mm f2...
But that's just me — everyone's priorities are different!
