| Nikon
D200 Review
by Digital Darrell
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Nikon
D200 IMAGE PROCESSING SYSTEM
Since
the Nikon D200 also uses the same 4-Channel RGB Image Processing
System as the Nikon D2x, it can create and process images
faster than most other cameras on the planet. Look at the
image below for a basic overview of the system:
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Nikon
D200 Image Processing System
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What
makes this system so powerful and fast is that the Red &
Blue pixels each have their own output channel, and the Green
pixels have two separate channels. Notice that each channel
has a small processor devoted to it. This processor prepares
the color and noise reduction while the image is still in
an analog form. After the image is optimized it goes through
the Analog to Digital conversion (A/D Conversion). Why is
this important?
Well,
if the D200 waited to optimize the image until after the digital
conversion, it would also be optimizing any artifacts and
noise that might accumulate during the A/D conversion process,
thereby amplifying image defects. Instead, the camera carefully
optimizes the image in its purest form, analog, then after
it is done, converts it to a very clean digital image. And,
since it does this using a processor for each channel, it
is VERY fast!
MULTI-CAM
1000 AUTOFOCUS SYSTEM
I
am particularly interested in the brand new Multi-CAM 1000
autofocus system. It has a similar 11-area AF sensor system
to the Nikon D2x/h. But, the cool new thing is that the sensors
can be combined into a 7-area “Wide” AF sensor
system. The AF modes are very similar to the Nikon D2x also,
with all four modes: Single AF, Dynamic AF, Closest Subject
Priority Dynamic AF, and Group Dynamic AF. This means that
the Nikon D200 will react more like the Nikon D2x than the
Nikon D70 in most lighting conditions. Nikon announced that
the D200's autofocus system is both “fast and precise,”
which is good news for people wanting to use the camera for
action photography.
In
a quick test, it is indeed very fast with AF-S lenses. Much
faster than the Nikon D70, faster than the Nikon F100 and
probably faster than the Nikon
F5 too. At least as fast as the D2h/D2x, and it locked
immediately into focus indoors. More on this when we can have
a body for more than a few minutes.
In
the 11-Area Autofocus picture above we can see that the actual
autofocus sensors are significantly wider than the AF brackets
in the viewfinder. Nikon has created a new mode as seen in
the 7-Wide Area Autofocus picture above. Since the AF sensors
tend to overlap anyway, why not simply add their signals together
into a wide area sensor array. This seems like a shortcut
to something similar to Group Dynamic autofocus, in my opinion.
It
seems that they have really worked on making the Nikon D200
a "fast and precise" focuser. The 7-Wide Area sensor
concept is made to help the D200 acquire moving subjects more
easily, and allows you to compose the image more effectively,
without the "focus and recompose" style needed by
most all AF cameras, including the D2x. The D200 one-ups the
Nikon D2x in this cool concept, in my opinion.
Looking
through the viewfinder -which is just a little smaller than
that on the Nikon D2x- as per the image above, it seems that
the Nikon D200 has one AF cross-sensor, while the rest work
in one direction only. A cross-sensor will work with both
vertical and horizontal subjects, while a normal AF sensor
works only in the direction it lies along. The center sensor,
which is the one most used anyway, is a cross-sensor, and
works in any direction. The rest work only in a horizontal
or vertical orientation.
Let's
look at the various autofocus modes in the Nikon D200, and
talk about how they work:
Single
Area AF - This AF mode is designed to pick
a single subject out of a complex scene and focus only on
that subject. One can use any of the 11-area or 7-wide area
sensors individually. The focus area in use is indicated
in the viewfinder. This mode can be used with both AF-S
and AF-C. (AF-S = Single; AF-C = Continuous Autofocus)
Dynamic
AF - Since all the AF sensors are in use
in this mode, it's best to use AF-C autofocus. As the subject
moves around in the viewfinder, the D200 will instantly
switch focus control from sensor to sensor, thereby tracking
the subject. In this mode one has no control over which
individual sensor is in use, since the camera's computer
is switching them around as needed.
Closest
Subject Priority Dynamic AF - This mode
is primarily made for things like portraiture in a complex
environment. If you are taking pictures of people or other
subjects, and the background contains objects that might
draw the attention of the autofocus system, this is the
best mode. It forces the D200 to ignore anything except
the closest and brightest object, which hopefully is your
subject.
Group
Dynamic AF - Consider this AF mode a "pattern
of action" recognizer. Let's say you are shooting a soccer
game, and you initially focus on a running person. The D200
will allocate a group of sensors to track the movement of
that subject, while ignoring other objects surrounding the
subject. This mode is good to use when a subject moves around
in the frame so quickly that it would be difficult or impossible
to use Single Area AF to maintain good focus. Within this
mode are two settings, "Dynamic" and "Closest
Subject," which work the same way the two primary modes
above, except that they are limited to the number of sensors
that Group Dynamic AF has selected to track the subject.
If
one learns to use these AF systems, one will have plenty of
flexibility in autofocus. No longer are we limited to just
Single Area and Dynamic AF, but instead have a range of powerful
autofocus modes making up the excellent Multi-CAM 1000.
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