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Nikon D2X AF
System Revisited
by Edward Erkes
tell
a friend about this Nikon Multi-Cam 2000 AF Module article
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IV.
Predictive Focus Tracking with Lock-On: Set via CSM a4
This
prevents sudden large changes in focus distance from causing
the camera to restart focus acquisition. It is designed to
prevent errors in focus due to either the photographer failing
to keep sensor on subject or another object briefly passing
between subject and sensor. Lock-on is enabled by default.
Previous Nikon cameras, such as the F5 and the D1X, had "Lock-on"
built into the AF algorithms. The Nikon D2x has added the
capability to turn it off, if desired.
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Custom
Setting Menu screens for a4 |
*I
usually leave Lock-On enabled in my photography. When I'm
photographing flying birds, I try to keep the active sensor
on the head and/or neck of the bird. However, this is not
always easy to do with a fast-moving subject. Lock-On prevents
abrupt loss of focus due to the sensor dropping off the bird
and onto the background. It also prevents loss of focus due
to a foreground object passing in front of subject. With flight
shots, the foreground object that passes in front of the sensor
can sometimes be the near wing of the bird as it flaps up
and down. If I disable Lock-On, I find that I more easily
lose focus on flying birds, especially if I'm using teleconverters
on my telephoto lens (especially with a 2X converter, where
initial focus acquisition is much slower).
Examples:
Nikon
D2X. 200-400AF f/4.0G VR lens with TC20EII teleconverter.
Dynamic Area AF with center sensor selected.
I
spent the better part of three days photographing a
pair of juvenile red-tailed hawks that allowed a closer
approach than any other hawks I've tried to photograph.
I
later learned that they had been born and raised in
captivity and just recently released to the wild.
I
had been photographing this hawk perched on a branch
when he suddenly swooped down to catch a small mammal.
Because
I was in AF-C mode and prefocused on the perched bird,
all three flight images were sharp—even though
I was using a 2X teleconverter.
Lower
photo with Nikon D2X, 200-400 f/4.0G VR lens, this time
with TC14EII. Group Dynamic AF Pattern 1 / Center Sensor
(Center group selected).
The
wildlife rehabilitator was still providing supplemental
feedings to the released hawks. He let me photograph
during one feeding. The bird dropped more than anticipated
when he left the branch, but predictive focus tracking
continued to function as the bird moved from the center
sensor onto the lower sensor. He was halfway off the
bottom of frame by the next shot and I totally lost
him on the following one. By cropping to more of a panoramic
format, I was still able to make a print with a nice
composition. |
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Nikon
D2X. 200-400 VR lens with TC20EII. Dynamic Area AF with
center sensor selected.
Top
two images were cropped for more pleasing composition.
With no foreground objects closer than the tundra swans,
one of the focus modes with Closest Subject priority
could have been used.
In
the lower photo, there is the risk that, as the swan
dropped further, a Closest Subject mode may have transferred
focus to foreground grasses (especially if a Pattern
1 group was selected).
I
didn't use a Closest Subject Priority mode in any of
these because AF acquisition is slow with a 2X converter
on the 200-400 and I get better results with Dynamic
Area AF and a user-selected sensor. |
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| Nikon
D2X, 200-400 VR lens with TC14EII. Group Dynamic AF, Pattern
2 / Closest Subject with Center 1 group selected. |
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You
may click on any image for larger view.
As
mentioned at the start, by carefully considering the various
options, how they interact, and one's own shooting style,
one can select from the many combinations and narrow down
the options for our own specific shooting situations and personal
style.
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