Of course the IQ loss is obvious, but considering the stacking I was expecting something much worse. So this is somehow impressive. I guess f/13 must have helped here.
Maybe the focus is a bit off from the eye? I have the feeling that I see more detail in the wing coverts than on the head (e.g. the bill). Or it could be a consequence of the 1/100 shutter. 1400mm must be quite a challenge to keep stable.
I agree with your assessment ... I forgot to add it was totally manual focus, I did miss it slighty and I tried a high f ratio because the dof is so slim at that focal length.
Right, I forgot to take that into account. For whatever reason my brain stuck in "1DMK4 auto-focuses with everything" mode.
I tried to focus manually once with my 100-400 and a 1.4x on a static subject. I tried hard. It was the last time of my life that I tried a manual focus