Laura asked:
"I`m looking for some advice. I have an F70 [with a Tokina f4.5 100-400
zoom] which I have been using for nearly a year to photograph retrievers at
work in the field ... but some of my shots are blurred, and I don`t know
whether it is through subject motion or camera shake."
It is quite possible that an N70 cannot focus-track on a running dog in all
circumstances. While AF speed and accuracy in this context is most limited
by the software and data processing power of the camera, your Tokina
100-400 may further limit AF speed due to its smallish aperture. If this is
the problem, the most blurry photos should be the ones where the dog is
running most directly towards you and has gotten within 30-40 feet, or
where it is running amid a complicated scene.
By the way, ignore the nonsense in Nikon manuals about focus tracking in S
mode. Use C mode for action.
But camera shake is also possible. 1/500 with a 400mm lens is not going to
work every time, or for everyone. The reciprocal rule is really for steady
shots, not when you are trying to follow jerky motion. Get yourself a
monopod, use faster film, relax, and avoid coffee.
As for motion blur, note that a dog running at 25 mph, 40 feet per second,
will move 40/500 ft during that exposure - about an inch (25mm). Depending
on how far away it is, which way it is running and if you are panning, this
may or may not translate into objectionable motion blur on the film.
Hope this helps.
Curt Austin, Cincinnati
http://www.AustinImage.com
