Monday, January 17, 2005

1D enjoys its first daylight outing

The 1D performed flawlessly at this weekend's three-way Pepperdine-UCSD-UCLA diving meet. The camera's motion-tracking auto focus (AI servo AF) was able to catch over 95% of the shots with tight focus. That's a remarkable rate considering that I shot nearly 900 frames on Saturday.

And it's even more impressive that it accomplished this with my 70-200mm f/4L lens. By AF standards an f/4 lens is adequate but not great. An f/2.8 lens (twice as bright) or an f/2 lens (four times as bright) gives optimal AF performance. To put f/4 into perspective, an f/5.6 lens (half as bright) is the minimum required for most AF systems. Beyond that most cameras will fail entirely. So f/4, while not terrible, certainly isn't doing the AF system any favors when it comes to the demands of fast action motion tracking.

The light kept changing as the sun moved from noon to 3pm, in and out of the tall trees adjacent to the pool. When the sun was on the divers its strong glare made the circular polarizer a necessity. It was able to tone down most of the glare and generally worked quite well (damn well better. That was a $120 piece of glass!).

This was also the first real test with the camera set up with some initially counter-intuitive button reassignments. The usual half-press of the shutter no longer controls auto focus. Instead AF is assigned to a thumb button - hold it down to AF on the subject or continuously track if in AI servo mode, then release to hold the focus as-is. The shutter half-press then becomes the auto exposure lock (AE lock). This is Custom Function #4, Option 1 (C.Fn-04-1).

In normal shooting this means: AF on your subject with your thumb, then point to an area appropriate for setting exposure and half-press and hold the shutter, then recompose and fully press to take the shot. Seems unnecessarily complex, I know.

But it makes more sense in action shooting. Your thumb controls when the camera will track the subject in motion. So if the subject stops, you can stop the AF system by releasing your thumb. Then you can recompose your shot and fire away. With the default button setup you would never be able to recompose - the motion-tracked subject would always have to be under your selected AF point (generally dead center). And no, you couldn't just switch from AI servo motion-tracking AF to normal one-shot AF on the fly. You'd have to hold down two buttons while shifting the control dial. It's just too cumbersome and would take too long.


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