kimknapp
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 p.7 #14 · A7rIV & 200-600 looks like issues may have been resolved | |
IMHO
Tips from a non-200-600 user for stationary birds (where you sometimes get back focus or poor focus):
1. Try NOT to use flexible spot. I have found, over and over, with the 600GM and the 100-400GM, that flexible spot can result in OOF shots, even when the spot is completely within a part of the bird that is in the correct plane. I only use it when the bird is buried in branches and then, if there is time, I switch to manual focus to get the focus tack sharp (difficult with the 600GM handheld because MF control is too coarse). I use zone AF almost exclusively and am often surprised how well it picks up birds even when there are branches nearby. Also, I think that since zone tries to get as many points in focus as it can, the focus point ends up in the middle plane of the front of the bird resulting in more of the bird being in focus. If you use zone in a busy environment try getting close to focus with MF first, as others have suggested.
I noticed this readily last weekend while photographing a very patient Great Horned Owl. He was in a tree and I was worried about a branch in front of him, so I started with small flexible spot. Over and over I had the spot right over the bill (very close to the same plane as the eyes) and the shots were too soft. I switched to zone and the shots were all tack sharp for most of the head (and a lot of the body). I have seen this over and over. For example, a while ago I posted a photo of a small bird sitting on a cross member of a wooden fence where I had put the spot on the bird and all of the spot was covered by the bird, but the camera ended up focusing on the fence's wall a couple inches behind the bird.
2. Don't bother trying to do BIF (even stationary birds sometimes) when lighting isn't low and behind you. I know that this is a basic rule, but I found it is much more critical with the 7Riv and the 100-400, so probably the 200-600, too. I am not sure what is going on, but I have found, over and over, that lighting from the side or front really screws up the focus. To prove it to myself, several times I switched to MF (stationary bird) and could get a tack sharp image, but AF was way off, even with zone AF. As just mentioned, even stationary birds can end up poorly focused in overly bright, side or front lighted conditions. I am not talking about mid-day heatwaves. And, I am not talking about extreme front lighting. This is much more evident in the 100-400 than the 600.
Just a SWAG, coming from an electrical engineering background with a lot of experience with radio waves, I suspect that enough of the light bounces off the inside of the hood and changes phase, that it confuses the phase detection algorithm. (any time a radio wave, including light, is reflected, the phase reverses). To be honest, I am not sure if this would affect the way the phase detection focuses, but... Would be nice to be able to turn off phase detect and only use contrast detect, just to see if it makes a difference. I may try an extended hood made from black felt to see what that does.
Just some thoughts. Hope they are helpful.
Kim
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. I meant on the camera, of course, since we were able to convince it that the FW update would make it perform like the A9 AF-wise. 
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