Quote Originally Posted by PatrickH View Post
Great shots. Do you think it is motion blur or focus? I ask because I see sharpness just beyond the plane of the head, back by the wing. I'm having my share of challenges with this. My goal is to place my focus point on the head, but for small birds that can be difficult. I'll often lock onto a larger part of the body.
Hi Patrick,

I think that is a great observation and now that I've looked at it a bit more, I think it is both may have been factors, which is a bit fascinating. I would put the sharpest point more at the shoulder/top of wing, which should not be that far off from the eye. Also, I do not see things getting progressively more blurry going from the head to tip of beak, rather I'd put those fairly consistent, which indicates it is somewhat parallel to the image plane. It seems the phoebe may have lunged not just forward within the plane, but a little to the side, closer to me. I do see a bit of directional blurr in the beak and, it is really tough to tell elsewhere.

Something that interests me is how "sharp" can vary. Playing with this example, DOF calculator online indicates I should have ~2.36 inch thick focus plane (700 mm, f/5.6, ~10 m away). But that side movement is less than 1.2 inches. Maybe 0.5"? Which, to an extent with something this small and detailed, but I don't think the same rules apply as to "critically sharp." I routinely see 5 images in a row all on a birds eye and you can see one that is in better focus.

But, yeah, little birds are a challenge. They move very fast, so this may be AF speed, shutter lag as well as shutter speed. If AF speed, I could potentially buy into the idea that a 1DX series body would be faster than my 5DIV. Shutter speed is something we can all adjust, at the expense of light on sensor. Shutter lag, hmmm, the 1DXIII rates it's lag at 29-55 ms while the 5DIV is 58 ms. Shutter lag doesn't get discussed much, but playing with the math, 58 msec is 1/17th of a second. 28 msec is 1/34.5th of a second. So, I wonder how much of the side movement happened in that 1/17th of a second?