I've used a catchy title to lure folks in. The attached photo has me curious as to what would cause the "Flying Donut" effect. The donuts are a flock of geese in the background. As you can see, they have been rendered as hollow circles, rather than as solid objects. Since I took the photo with a D7000, I thought I'd post here. The settings were D7000, 70-200 VII lens and the new TC2.0III at f8, 1/2500, -1.3EV and ISO 320. I was facing SW at 4:45PM. One dozen of Dunkin' Donuts finest for the correct answer. Richard
#1. "RE: Flying Donuts" In response to Reply # 0 Wed 16-Feb-11 07:01 PM by gkaiseril
Bokeh! The geese are further than the far acceptable focus distance for the focused distance, part of DOF, so they become part of the Bokeh or area beyond the far acceptable focus point and appear out of focus.
#2. "RE: Flying Donuts" In response to Reply # 0 Wed 16-Feb-11 07:59 PM by chris_platt
Interesting. Maybe that is what Thom Hogan was talking about:
"Are there times when it shifts where it imparts a change to the image quality other than pure stabilization? I believe there are, though the impact is visually subtle. Some of the mid-range distance bokeh of certain VR lenses appears to be impacted by VR being on. Put another way, the background in the scene is slightly moving differently than the focus point in the optical path. This results in what I call "busy bokeh," or bokeh that doesn't have that simple shape and regularity we expect out of the highest quality glass."
I too have your exact setup. I noticed the Bokeh to be more exaggerated while using the tcIII. Try it without and you will see what I mean. It looks more like the iris circle of the lens is some of my images. I really think I can count the aperture blades in some of my Bokeh images. Can someone explain that to me please. Also the CA is much more pronounced. But that setup still focuses very fast in good light and is tack sharp.
Hi Folks: thanks for all the replies. Bokeh does render objects such as Christmas lights, brightly lit leaves etc as bright circles and we're evidently seeing the same thing here. I was surprised though, to see the geese rendered as dark, hollow circles however. Robman3-the plants are commonly called Mullen or Flannel Plant. They are a very successful invader here in Denver as well as elsewhere in the West. The donut winner is GKaiseril. Please call when you're next in Denver. Richard