Цитата:от:Николай Мартыненко
Вот это кажется чем-то таким, что уже можно пощупать. Тобишь вразуметь. Значит, я активирую НЕ крест а просто один из ВСПОМОГАТЕЛЬНЫХ датчиков рядышком? Я правильно понял? И поскольку он значительно меньше креста, то не зацепит витрину рядом? Правильно? А вспомогательные датчики БЕЗ основных крестов вообще сами по себе по штучно работают?Подробнее
НЕТ, НЕПРАВИЛЬНО!!!
В автофокусной системе D3/D700 имеется 51 датчик. Из них
15 крестообразных и 36 горизонтальных.
15 крестообразных датчиков занимают центральную часть: они расположены тремя центральными вертикальными рядами по пять в каждом ряду. По краям от них (справа и слева) расположены горизонтальные датчики группами по 18 штюкк.
Дальше привожу цитату из руководства Хогана по D300 по выбору зон автофокуса (извините, но на Инглише). Она полностью действительна и для D700:
Single Point AF—the camera uses only the currently
selected autofocus sensor for focusing. You control which
sensor is used to focus by pressing the keys of the
Direction pad on the back of the camera (when the meter
is active).
Dynamic Area AF—the camera starts by focusing on
the subject under the currently selected autofocus sensor,
but if Continuous Servo AF is set, may use another sensor
if it detects that the subject is moving. You control which
sensor the system starts focusing with by pressing the keys
of the Direction pad on the back of the camera (when the
meter is active). You also control how far from the
selected autofocus sensor the camera will follow a moving
subject (9, 21, 51, or 51 3D, set via Custom Setting #A3).
Auto Area AF—the camera always determines focus
by itself, based upon a number of factors, including a
crude face recognition scheme if you’re using G-type or
D-type lenses (which supply distance info to the camera);
you get no choice in which autofocus sensor will be used
for focusing; the camera evaluates all fifty-one sensors.
It should be clear that Single Servo, Single Point is straightforward: the
camera only focuses on the spot you pick, and the camera won’t shoot until focus has been achieved. This is a very good
starting place to get acquainted with using the Direction pad
to control the initial sensor and for getting predictable
focusing results, even if you focus and reframe (remember to
keep the shutter release halfway down after achieving focus if
you reframe, though).
The next step I’d suggest is to pick Single Servo, Auto Area.
This combination doesn’t allow you to pick a starting point,
but it will show you what the camera chooses for a focus
point. You’ll start to see how the camera recognizes objects
and patterns. This should give you some confidence to take
the next step: switch to Continuous Servo, Auto Area. The
camera is still picking focus, but now it’s also using predictive
focusing for moving subjects. Unfortunately, this combination
does not show you which autofocus sensor(s) ultimately gets
used, but that’s why I had you start in Single Servo to get
confidence in what the camera is picking.
Finally, choose Continuous Servo, Dynamic Area. Now
you’re telling the camera where to start focusing (you pick the
initial sensor) and the camera follows moving subjects using
its predictive methods. You still have one primary option to
set: Custom Setting #A3 tells the camera how far away from
the initial sensor you’ll allow it to move the focus (9 points,
21 points, or two versions of 51 points). If your subject is
nearly full frame, then 51 points is what you want. But if
you’re following a smaller subject where there are other
possible subjects—such as following a single player on a
football field—you might want to narrow the camera’s
attention to a smaller number of sensors.
Autofocus Settings Summary
The big problem most first time D300 users have is that this is
a very different system from previous Nikon cameras. In
particular, I see these aspects causing the most confusion:
Single Servo no longer uses predictive focus. A subject in
motion when AF is first detected is not tracked on a D300,
where it was on many previous Nikon models with this
setting.
Group AF is gone. None of the variants of Group
autofocus appear on the D300 as they did on the D200
and D2 series. There is also no Wide/Narrow choice nor
any patterned groups. If you were using one of these
options, you’ll have to convert to a new technique.
Closest Subject Priority (CSP) is gone. As much as I’ve
harped on negative aspects of CSP, there certainly were
times when it was useful. The D300 has no method in
which you can force it to focus on the nearest object or
nearest object in a group of sensors. Again, if you were
using those facilities on your previous camera, you’ll need
to find a new method.
The camera doesn’t always tell you which autofocus
sensor was used. See the summary chart, above. In most
Continuous Servo modes the camera doesn’t tell you
which area was used for focus. Over time you’ll learn to
trust the camera, but until you do, remember that you can
always review the focus selection point after the fact by turning on Focus point using Display mode on the
PLAYBACK menu and then navigating to the page that
shows that information during image playback.
There’s good news, too:
Focusing can occur over a large area. Only the D2 series
•
can claim to cover as wide an area of the image frame as
the D300, and those earlier cameras had gaps in the
middle of their coverage that the D300 doesn’t have. The
D300 can focus on subjects far more off-center than can
its predecessor, the D200.
Low light performance covers a wider area. The fifteen
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crossed sensors in the middle of the autofocus sensor
array cover a wider area than those in the D200 or any
other camera Nikon has made. Even the D2 series, which
had nine very large crossed sensors scattered over the
frame didn’t quite cover as much contiguous area for low-
light performance as the D300.
Focusing is integrated with metering. The reason why Auto
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Area is so good at recognizing people in a frame has to do
with the integration with the metering sensor, which
provides the color information that tells the autofocus
system where skin tones occur in the frame. Likewise, if
you select 51point 3D tracking, the meter provides pattern
recognition information to the autofocus sensors, which
helps them determine where in the scene your subject has
moved.
One important thing to note: in terms of user control, the
Autofocus Area settings range from total (bottom selection on
the control switch: Single Point) to none (top selection on the
control switch: Auto). If you find that you don’t have enough
control of the sensor area used for focusing, try using the
Autofocus Area mode setting immediately below the one
you’re using!
Trap Autofocus
If you’ve used a Nikon film SLR, you may have encountered a
special autofocus mode called “trap autofocus.” On some
bodies, this was only available with the multi-function back,
while in others it was available through custom settings.
Trap focus is a situation where you prefocus on a particular
spot and no picture is taken until something occupies that
spot and is noted as being in focus. For example, you focus
your camera for the finish line of a race. But until someone
hits the finish line and is seen by the camera to be in focus,
no picture is taken. The moment that first racer does hit the
finish line, click, your picture is taken.
You can mimic trap focus on a D300 (Custom Setting #A2
cannot be set to Release):
1. Set Custom Setting #A5 to AF-ON Only.
2. Set the Focus mode to Single Servo.
3. Set the Autofocus Area mode to Single Point.
4. If the lens has a focus switch on it, set it to A
(Autofocus; on some lenses this is labeled M/A).
5. Pre-focus the lens to a particular distance.
6. Press and hold the shutter release. The camera shoots
when the selected focus bracket is in focus
(remember, you can also use the AF-ON button to
focus).
Lock-On (Focus Tracking)
The D300, like all previous Nikon bodies, has the tendency to
hold focus at an established position when objects move in
front of the object being focused on. This trait can also show
up as an inability to follow focus on something that’s jumping
big distances between shots when you’re a using Continuous
release shooting method and Continuous Servo AF. Custom
Setting #A4 (see page ) gives you the ability to fine tune
this function.
More so than previous Nikon bodies, you may find that you
need to shorten or remove the Lock-On value to satisfactorily
follow focus on subjects moving towards you. If you’re getting
poor follow-focus results on moving subjects, this is the first
control to change.
The Pro Approach to Autofocus
Many professionals gravitate to the same approach to
autofocus (which I’ll describe in a moment). The reason is that
changing autofocus settings all the time can be a tedious
process, as the autofocus controls are split between a switch
on the front of the camera, a switch on the back of the
camera, and the Custom Setting menus. Thus, most pros look
for a single menu setting combination they can use that gets
them 90% of their autofocus needs and helps them avoid
menu-itis.
The solution is the AF-ON button on the back of the camera.
Specifically, here’s what you do:
• Use Custom Setting #A5 to move autofocus activation to
AF-ON only.
• Set the switch on the front of the camera to C (Continuous
Servo).
• Make sure that Custom Setting #A1 is on the default of
Release.
Now your camera is configured to autofocus only when you
press the AF-ON button. This provides you with the following
abilities:
Focus and reframe. Focus on your subject using the AF-
•
ON button, let go of the button, then reframe. Focus stays
where it was when you let go of the AF-ON button.
Track focus. Just hold the AF-ON button in while
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shooting. Focus will be performed as usual. This takes a
bit of dexterity, as you have to hold the AF-ON button in
at the same time as pressing the shutter release.
Manually focus. With most AF-S lenses, just twist the
•
focus ring. On other lenses, move the lens’ focus switch to
the M position first.
This means that the primary control you change—if you make
any change—is only the Autofocus Area selector switch on
the back of the camera. Switch to Single Point for focus-and-
reframe, to Dynamic Area or Auto Area for tracking focus,
depending upon the subject. (Note that you can assign
Dynamic AF Area settings to the Fn button on the front of the
camera via Custom Setting #F4.)
Using this technique takes practice, so don’t expect to make
those settings and rush out and take perfect pictures a few
minutes later. However, with practice it becomes second
nature and relatively easy to control your focus in most
situations without having to make multiple settings changes.
