Originally posted by ivanvernon I recommend the FA400, just a little less sharp than the FA*300, but not much. I hope you like using tripods more than I do or don't mind running up the ISO to get a faster shutter.
I have both the FA 400mm 5.6 and the FA 300mm* 4.0 and when I got the 300mm* I left the 400mm in the dry box for a long time. The other day I dug up some old pics I took on safari with the 400mm and found the sharpness beyond what I could remember it to be. So I did a couple of test shots on a building about 130m from my house and it has a brick pattern facade. What I found was that the 400mm was actually marginally sharper then the 300mm* but it has more CA. The 300mm* has markedly less CA, for just about the same sharpness.
A little about the tripod(s) I use, I know it slightly off topic, but sort of related: I have a Gimbal (Nest brand) mounted on a heavy duty beast (Leofoto brand, dont know the model) which I rarely carry with me these days and a lighter travel with (Rollei R364C), which works just as good. For the low shots I use a small Berlebach without a head, the camera screws directly onto the tripod's swivel top, if you choose to do so.
Because both the 300* and the 400 are not particularly heavy in comparison with the camera, I mount the camera on the gimbal and don't use the lens tripod mount. This causes a slight tension on the whole mount, which has a dampening effect on the vibrations. Made a huge difference when I accidentally discovered this.
So in conclusion I am truly torn between the 400mm and the 300mm* because the 400mm does give you that little bit extra reach for essentially the similar sharpness, whilst the additional CA is maybe not that much. I tried both of these lenses on the 1.4tc and the 2.0tc and I found it underwhelming.
Lenses I can recommend are the FA 150-300 zoom and the A* 600mm. I use the 600mm* on safari with a gimbal and monopod in the safari vehicle on the go as well. A bit clumsy in the beginning, but you soon get your rhythm.
The picture below was taken in 2016 with the 150-300 at 300mm with about a 30% crop 1/250 f8.