that is supposed to make life easier, autofocus seems
to stymie a lot of people, especially those who are
starting out with SLR cameras. And usually, it is the
poor, innocent SLR that takes the blame, while all the
crotchety old-timers sit in the corner and shake their
heads knowingly, muttering something about new-fangled
For starters, autofocus, like any
other camera feature, only works effectively when you,
the user, control how it works. Letting the camera decide
where to focus is like taking relationship advice from
the Penthouse forums – it may sound really tempting
but has a snowball’s chance in hell of working
on this planet.
So the first step in focusing properly
is to take control. Your SLR most likely has between
3 and 45 focusing points. It also likely has a mode
whereby all the focusing points are active, and the
camera selects where to focus from one of these points.
This is the mode you NEVER want to be in. For starters,
your camera doesn't know where you want the focus to
be (it cannot read minds yet, although the next Canon
SLR is rumored to---- ). Second, maybe your desired
point of focus is not where the sensors lie.
What you want to do is pull out you
camera manual, open it to the page where it talks about
focus point selection, and read up on how to manually
select focusing points. Usually, this involves pressing
a button and/or moving a joystick or arrow keys (or,
if you are lucky, eye-controlled focus). Now go ahead,
practice. Get it down pat, so that you are able to select
and change between focusing points without fumbling
around or taking your eye off the viewfinder.
Once you have that down, let’s
move on. For the rest of this chapter, whenever we talk
about focusing, we are referring to you, the user, actively
choosing an autofocus point, placing it on top of your
subject and then choosing to focus on that spot.
Getting started: Focusing
on stationary objects
Most cameras have at least 2 autofocus
modes – one is called “One Shot AF”,
the other “Continuous AF” (or Predictive
AF). The exact term may vary from camera to camera but
the concepts are same. For now, where you are shooting
stationary objects, One Shot mode is the one you want.
In this mode, select the AF that you
want, put it on top of the subject and half-press the
shutter – this causes the camera to focus on the
part of the image on the selected AF point is resting.
Now, as long as you keep the shutter button pressed,
the focus stays locked on that point. This lets you
move the camera around and recompose the scene if need
be, until you get it exactly the way you want it. Thus,
you can put your subject wherever you want – even
someplace that is not covered by an AF sensor.
Once you have the composition the
way you want it, press the shutter and you’re
Sounds easy, doesn’t it? Well,
it is. With practice, you’ll find it takes a fraction
of a second to lock focus, recompose and shoot.
One side benefit of this is that you
no longer need a lot of AF points. All you need is 1
AF point - this “focus-lock-recompose” method
then lets you put the subject wherever you want. A lot
of people – myself included – don’t
need anything more than a single, central AF point when
shooting this way.
Do note that in the One Shot mode,
the camera will not let you shoot until the focus is
locked. Also, if the subject moves once you have locked
focus, you will need to re-focus. Lastly, if the subject
is close to the camera and you are using a large aperture,
the act of recomposing may cause the subject to move
out of the plane of focus. However, in the vast majority
of cases, this approach works very well and has stood
the test of time.
Moving along: Focusing on
Well, if the first part was easy,
the second part is a fair bit harder. It is like going
from a bicycle with training wheels straight to a 950CC
MotoGP superbike. Ok, maybe it is not that bad, but
it is a bit of a jump nonetheless.
As mentioned earlier, all modern SLRs
also have a “continuous autofocus” mode
(or whatever it may be called). Here, half-pressing
the shutter and keeping the sensor on the subject causes
the camera to continuously keep focusing on the subject,
tracking it even as it moves. Not only that, the camera
even takes into account the time delay between the pressing
of the shutter and the taking of the picture, and adjusts
the focus to account for the subject movement in that
fraction of a second. How’s that for cool?
In theory, this whole process is easy
enough: simply keep the selected sensor on the subject
and keep the shutter half-pressed, and shoot when you
But this is where the complication
arises. Because the subject is moving, you have to follow
the motion with your camera. The faster or more erratic
the movement of your object, the harder it is to accomplish
this. Your goal is to try to pan with the subject in
a smooth, continuous motion - and gaining the ability
to do so requires practice.
For the most effective results, continue
panning not only until you’ve pressed the shutter
but till a little after that (till you can see the subject
again in the viewfinder) – this ensures that you
don’t break your rhythm at the time of taking
the shot. Also, in order to increase your chances of
an in-focus image, track the subject for at least a
couple of seconds before clicking the shutter.
Panning is but one aspect of shooting
moving objects. In continuous AF mode, “lock and
recompose” does not work, so you have to activate
the appropriate auto-focus point and keep it on the
subject. That, of course, makes composition harder –
if you use the central AF point, you are putting your
subject dead center: a compositional boo-boo. On the
other hand, if you move your subject off-center, you
run the risk of not having an AF point at the appropriate
place in the frame. And of course, your subject has
to fit the frame as well.
So now let's break the first rule
we laid down while discussing autofocus.
If your subject is against a uniform
background (like a flying bird against the sky), or
is large enough to cover a significant portion of the
frame, select all the autofocus points and let the camera
pick (this is the one time it is ok). This makes it
a lot easier to keep focus on the subject and also makes
it easier for the camera to track the focus. However,
you run the risk of the camera selecting the wrong point,
true – for example, focusing on the bird’s
body instead of its head and eyes. If the subject is
some distance away, this usually isn't a problem. Also,
if you are shooting against a uniform background like
the sky, you can also stop down a little more for additional
depth of field to compensate for this.
Do note that this above technique
only works properly against a uniform background - try
it against, say, foliage, and you're in for some serious
frustration. If your sensor comes off the subject, your
camera will try to refocus (and out of sheer spite,
will choose the wrong focusing spot, causing your subject
to blur out and your lens to start hunting).
In such cases, it is often easier
to select the central focusing point and keep it on
the subject. This gives you room in the frame and prevents
accidental cropping of the subject. You can always modify
the composition by cropping the final image later. As
you get better, you can move on to selecting an off-center
point and putting it on the subject - but this only
works if you can be sure of not accidentally cropping
off part of the subject.
The secret to successfully shooting
moving objects lies in one word: practice. There are
no short-cuts – this is simply a matter of keeping
at it. If you have a DSLR, you are lucky – practice
is free. If you have a film SLR, buy large quantities
of the cheapest film you can find… or initially,
practice without any film in your body. Start out with
easy to track subjects – like people walking.
Then follow faster objects, but with predictable movements.
And then move on to tricky stuff – like flying
birds, playing puppies, etc. The good news is that modern
AF systems have become so good that this skill is within
grasp of most of us.
This mode is best used with your camera’s
drive mode set to continuous shooting. Most SLRs these
days can chug along at a very respectable 3-4fps at
the very least – that gives you a fairly good
chance of capturing exciting action sequence. You’ll
never get all shots sharp and in focus, but with practice,
you’ll get enough keepers.
Attaining guru status: Advanced
Ok, so now you know how to focus stationary
objects and moving objects. But what if you don’t
know whether your subject will stay still or move? If
your subject was stationary, you’d want to lock
focus and recompose for the best composition. On the
other hand, if your subject suddenly started moving,
then you’d have to pull your camera down, change
focusing modes and then re-shoot. By then, you’ve
lost your shot. On the other hand, if you stay in continuous
focus mode, you wouldn’t be able to recompose
– the very act of pressing the shutter to take
the shot would cause the camera to recalculate focus.
That’s quite a dilemma, innit?
Well, technology and intelligent design
to the rescue. With mid-end and higher Canon –
and presumably also with Nikon – SLRs, there is
a button in the back called “Auto Exposure Lock”,
usually denoted with a “*” – pressing
this locks exposure. However, by changing one of the
custom functions (CF4 for Canon), it is possible to
assign autofocus to this button, instead of the shutter.
The shutter is then used to lock exposure.
If you shoot a lot of action, you
want to do this (by setting CF4 to either 1 or 3 for
Canon bodies). And keep your autofocus mode set permanently
to “Continuous” mode.
Now, let’s say you have a stationary
subject. Point the camera over to it, press the “*”
button and your camera autofocuses on the subject. Release
the * button and you can recompose to your heart’s
liking – all the benefits of One Shot Autofocus.
If the subject starts moving, all you have to do is
put your selected AF sensor on subject and press the
“*” button again to track focus. –
all the benefits of Continuous Autofocus.
One of the biggest annoyances of shooting
with a big telephoto is its tendency to re-focus everytime
you press the shutter button. By using this mode, the
camera only focuses when you want it to focus –
the rest of the time, it behaves like a manual focus
Yep, you do have the best of both
worlds. Ain’t technology great?
Another trick you can try, if you
want and your camera lets you, is programming one of
the rear buttons on your SLR to switch to a “favorite”
focusing point. For example, my default focus point
on my SLRs is the center point; however, I have one
of the rear buttons programmed to switch to all AF points.
Thus, if I am shooting and find the
center point is not enough in helping me track the subject
(either it is too small, or moving too fast), then I
simply press this rear button and all 45 points on my
body come alive and start tracking the subject. I can
do this while in the middle of following the subject,
and without taking my eye off the camera.
Common focusing errors
Still having problems? Before accusing
your SLR of having faulty focus, going back to manual
focus, or worse yet, blaming me, consider the following:
• If you are panning the camera
or your subject is moving, it will appear at least partially
blurred, unless you are using a high shutter speed (how
high depends on how fast the subject is moving, how
far it is from you and its direction of motion). This
isn’t always a bad thing – a little bit
of blur implies motion and makes the image more dynamic.
• Even if you focus correctly,
if your shutter speed is too low, you will get somewhat
blurred results due to camera shake. The old rule for
getting sharp results while handholding is to keep the
shutter speed equal to, or faster than, the inverse
of the focal length. So for a 300mm lens, you’ll
want to shoot at 1/350 or faster.
• If you are using a telephoto,
then you don’t have a lot of depth of field to
play with. Moving your AF sensor even slightly off your
desired point may cause your image to appear improperly
Furthermore, depending on your subject’s
size and how close you are to it, even a properly-focused
photo may not yield the entire animal sharp from nose
to tail. This is because you don’t have enough
depth of field. If that is the case, consider stopping
down your aperture to increase your depth of field.
• If you are shooting macro,
don’t bother with AF. Use manual focus.
I hope this tutorial is useful - if
you have any comments, please feel free to email me.