Action at dusk

I took this picture of a leopard in Botswana. We came upon the cat after sunset, and after a few minutes I saw it crouch in anticipation of some kind of leap. I told my photo tour group to expect action and to select a shutter speed fast enough to freeze this kind of movement. Also, I said, watch the subject through the viewfinder because when the action occurs, it's going to be fast. When the leopard finally leapt, I fired at 4 fps -- the fastest frame rate I had at the time on a Canon 1Ds Mark II. The light was low and when I took this 20 years ago, I was still very much concerned about noise. That's why the ISO I used wasn't high -- it was 640. And that's why my shutter was only 1/200th of a second (and the aperture f/5.0). Photographing a leopard leaping from one branch to another is not like trying the freeze the wings of a small bird, so I took a chance and, fortunately, this shutter was fast enough to produce a sharp image. Had I taken this now, I would have used a shutter of 1/500 to be safe. Because I was shooting toward a bright sky, the original background was solid white. It's pretty bad, so I replaced it with the kind of sky I really wanted. Strangely, I took this with a 50mm lens. I haven't carried this with me for years.