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Understanding
Multi-CAM 2000 Autofocus
by Digital Darrell
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RELEASE
PRIORITY VS. FOCUS PRIORITY
First, let's consider a couple of custom settings that cause
more users to get slightly out-of-focus images than might
be believed. They're Custom Settings “a1”
and “a2,” which set the camera to either
FOCUS PRIORITY
or RELEASE PRIORITY.
These apply to AF-C or Continuous Servo AF and AF-S or Single
Servo AF. AF-C uses custom setting a1, while AF-S uses a2.
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Rufous
Hummingbird by Nikonian Ron
Green
D2X + 600mm Nikkor, f/11 @ 1/250, ISO 320, external strobes |
FOCUS
PRIORITY simply means that your camera will
refuse to take a picture until it can reasonably focus on
something.
RELEASE
PRIORITY means that the camera will take a
picture when you decide to take it, WHETHER ANYTHING IS IN
FOCUS OR NOT! (Read the last paragraph again, until it sinks
in)
Now,
you might ask yourself “why is there such a setting
as Release Priority?” Well, many photographers are shooting
high-speed events at high-frame rates, taking hundreds of
images, and are using depth-of-field (or experience and luck)
to compensate for less than accurate focus. They are in complete
control of their camera’s systems, having a huge amount
of practice in getting just what they want from their cameras.
And,
for many pro photographers, the camera’s choice of focus
points are not what the photographer wants the camera to focus
on, so they override the focus using various means.
Here
is a quote from a professional D2x user on why he rarely uses
Focus Priority:
“I
want what I want in focus and not what the camera wants in
focus. Let me give you a few examples. Many times, the part
of an open wheel race car which has the most ‘edges’
for the camera’s brain to focus on, is the nose and
front wing with all of the decals and sponsor’s names
and suspension parts. Many times, what I want in focus is
the helmet. A lot of times, if you are in “focus priority
mode” the camera will not fire when it is focused on
the helmet… I do not want the camera to tell me I can’t
take a picture when what I want to be in focus is in focus,
even though it may not be what the camera thinks should be
in focus. I want to be able to take when I want to take, and
I want what I WANT to be in focus.” John
Cote
So,
clearly there are very valid reasons for photographers to
not use Focus Priority. But, most of those same photographers
do not let the shutter release button start the autofocus
either, since the focus would change every time the shutter
button is pressed. These photographers usually set Custom
Setting a5 so that the autofocus does not even activate until
the AF-ON button is pressed. (see D2x manual page 185)
You
need to ask yourself, “What type of a photographer am
I?” If you are a pro shooting fast race cars, focus
priority may not be for you. But, for the average photographer
imaging his kids running around the yard, deer jumping a fence,
flying birds, or a bride tossing a bouquet, Release Priority
may not be the best choice. For many it is better to have
the camera refuse to take the picture unless it is able to
focus on your subject. For most then, Focus Priority is the
best setting.
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