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In my earlier tutorials on photographing wild birds I have covered
points 1 to 3 in my list of common errors:
1) Subject too distant.
2) Subject not in focus
3) Blur due to subject movement - motion blur
4) Blur due to camera movement
5) Incorrect exposure
6) Little consideration given to lighting or composition
Let's now carry on moving down the list and finding counters to
these issues.
4) Blur due to camera movement
In the last tutorial we looked at the affect of
blur due to subject movement. Now let's move onto blur caused
by unwanted camera movement and vibration.
Let's face it, nobody likes using a tripod, monopod,
beanbag or other means of support as they add extra weight for
us to carry and also restrict our movement. What they do achieve
though is to eliminate most sources of our own camera shake and
vibrations present within the camera.
Is it always necessary to use a camera support ?
The answer is no, but it depends on a number of factors: The magnification
(how large the subject is in the frame) and is therefore is related
to the focal length of the lens in use, how high a shutterspeed
we have available to us, whether the lens has image stabilisation/vibration
reduction (IS/VR) and finally the size of the cameras image sensor
employed.
Try mounting a recent camera and long lens onto a tripod and view
the rear screen in Liveview mode. If you then increase the zoom
to around 10x , focus manually and look at the image you will
notice that if you so much as touch the camera very lightly the
image vibrates wildly on the screen. Imagine what will happen
if you were handholding. This is camera shake and we must eliminate
it if we are to get critically sharp images, but at what shutterspeed
can we safely ignore this issue?
With film cameras, the accepted wisdom was that you can handhold
at the reciprocal of the focal length of the lens. In other words
if you are using a telephoto lens of 500mm focal length you should
ensure that you have a minimum shutterspeed of 1/500 sec. A full
frame sensor camera with a 35mm sensor should be equivalent to
a film camera with 35mm film fitted so the same wisdom should
apply.This guideline is a pretty good rule of thumb, but assumes
that we can all handhold a camera and squeeze the shutter gently
to the same degree. Of course we can't, so it is worth doing some
experiments to determine what you can achieve with your own gear.
The guidance also needs to be updated to reflect IS/VR systems
built into cameras or lenses. These can very usefully enable you
to handhold at a shutterspeed of between 2 and 4 stops slower
than you could without it. A Canon 300mm f4 IS enables you to
theoretically handhold at 2 stops lower, so that means you could
hand hold it when fitted onto a film or full frame camera at 1/300
sec without IS (so the nearest shutterspeed is 1/250 sec) and
1/60 sec with IS employed. This is a huge advantage and when combined
with modern cameras' high ISO abilities a tripod is become less
of a necessity unless trying to freeze motion, shoot at small
apertures or in low light such as in a forest or on a dull day.
You still need to bear in mind though, that although you you may
be able to hold the camera to lower shutterspeeds, the subject
movement remains the same so motion blur is still a possibility
that you need to factor in.
The crop factor of the camera must also be considered. Cameras
come with 1.3x, 1.5x or 1.6x crop sensor sizes which increase
the effective focal length by the same factor. Our 300mm f4 lens
that could just about be handheld at 1/250sec (without IS) becomes
effectively a 480mm lens on a 1.6x crop camera so you should not
handhold below 1/500 sec.
When I am photographing birds I usually use a 500mm f4 IS lens
which I use with or without teleconverters, so the use of a tripod
and head is usually essential. The weight of the equipment is
such that it can be hand-held if there is sufficient shutterspeed
available but only for short periods unless you have the muscles
of a weightlifter!
When shooting birds in flight I like to use the Canon 400mm f5.6
lens as it is very sharp, is fast to autofocus and comparatively
compact and light in weight. It does lack IS, but as you need
to be shooting at high shutterspeeds anyway to freeze subject
motion this is not much of a handicap. The Canon 400mm f4 DO IS
is even better as its maximum aperture is a stop faster and the
IS makes it more versatile for other uses.It is however considerably
more expensive and probably has no better image quality than the
f5.6 lens.
Camera vibration
If you put your teeth on the hot shoe on the top of the camera
and take a picture you will feel a pulse of vibration as you fire
the shutter. This is caused by the mirror being flipped up and
down when the camera takes the picture. Unlike the low frequency
movements of camera shake, this vibration is a very high frequency
movement within the camera and can cause softening of the image
if not controlled.
You would think that you would get your sharpest images by mounting
the camera on a tripod and by using a remote cable release, instead
of pressing the shutter button by hand. Thanks to the internal
vibrations that I mentioned previously this is not actually the
case. The vibrations are in fact amplified by travelling from
the camera, up a long lens, through the lens hood and back down
to the camera sensor. It is important to damp this vibration by
using good long lens technique which is described in the next
section.
If you are using incredibly slow shutterspeeds in the order of
1/10 second for some reason, or you are using stacked converters
on a long lens to get maximum reach it may be beneficial to lock
up the camera mirror (Using Mirror lock-up MLU - usually found
in the camera custom functions). An alternative is to use liveview
as the mirror needs to be raised to enable you to look at the
image straight off of the sensor. If you now use a cable release,
the camera operates very quietly and smoothly causing much less
unwanted vibration. Camera models can behave differently in liveview,
so I recommend you read this excellent article by
Juza on the subject if interested.
Long lens technique
When using a long lens on a tripod you need to damp
the internal vibrations caused by firing the shutter as follows:
Stand with your feet hip-width apart to get a good
stable stance and then grip the camera grip with your right hand
as usual with your index finger gently resting on the shutter
button.Now look through the viewfinder and press your eyebrow
up against the rubber eyecap and press your cheek gently into
the camera. Next, place your left hand on top of the lens directly
over the pivot point (the ball head). Now lean your weight on
your left hand. You are now grounding those vibrations through
your body and image sharpness will benefit as a result.If you
would like to read more about long lens technique click here:
Nature
photographers online magazine article
The great American bird photographer, Art Morris
has a variation on this method which may be worth trying:
" With the palm of your left hand pointing skyward, put that
hand under the front of the lens plate and grab it with the last
two or three fingers. With your thumb and index finger, push up
forcefully on the lens barrel from below. (No matter how sturdy
your tripod head and big lens are, there will always be some play
here.) You may have to frame a bit low so that when you "take
the play out" you wind up with the desired framing. Hold
the camera firmly in your right hand and press your face against
the camera back and you will be able to make sharper images at
slower shutter speeds than ever before."
Art Morris also uses this
technique for the Mongoose 3.5 head and says that it is similar
for the Wimberley heads.
Finally, whichever method you choose, when you
want to take a shot,don't jab at the shutter button (not always
easy when something exciting is happening in front of you). Instead,
simply increase the finger pressure until the shutter fires.Some
good bird photographers describe using a rolling motion of your
index finger.
IS/VR on or off on a tripod ?
On the first generation image-stabilised
lenses the manufacturers advise that you switch the IS (VR) off
when using a tripod. The reason for this is that the stabiliser
can hunt around looking for motion to stabilise instead of just
staying still. If you look through the viewfinder you can see
this wandering movement if you lock down the ball head firmly.The
Canon 100-400mm f4.5-5.6L IS is an example of a first generation
IS lens that behaves in this way. I always turn IS off on this
lens on a tripod.
In 1999, Canon announced a new generation of super
telephotos with second generation IS. The stabiliser used in the
300mm f/2.8 L IS USM, 400mm f/2.8 L IS USM, 500mm f/4 L IS USM
and 600mm f/4 L IS USM offers a 2 stop advantage and does not
have to be switched off when used on a tripod.
With these lenses it is claimed that IS helps to
combat wind or ground vibrations and also mirror slap. The IS
should therefore be left on permanently. I normally heed this
advice when using a a ball head that is tensioned but not locked
down and also when using a gimbal head (which effectively floats
weightlessly). However, if you lock the head down tightly you
will still see the image wandering around in the viewfinder. It
is only moving very slowly, so if you are using a shutterspeed
in excess of 1/125 sec I don't suppose this movement is significant,
but at lower shutterspeeds I am inclined to turn IS off again.
When working hand-held, off of a monopod or bean bag, I always
leave IS on regardless of the lens in use.
Lens IS modes 1 and 2
Finally some image-stabilised lenses have a switch to
control whether IS is on in both planes (vertical and horizontal)
or just in the vertical plane. The manufacturer advises that position
1 (both planes) is the usual position and position 2 is only used
when panning. The idea is to stop the stabiliser opposing your
intentional horizontal movement when panning. Some bird photographers
claim that position 2 is the one to use all the time as it acts
like position 1 until a horizontal panning movement is detected.
I am not sure whether this is correct or not. Others claim that
position 1 is the one to use for birds in flight (BIF) as the
IS works as described by the manufacturer and you are rarely performing
a true pan - as birds are either coming towards you or at a forward/sideways
angle, rarely do you pan like you would if you were photographing
a racing car going past you. You therefore need stabilisation
in both planes - so position 1 is the one to use.
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The stabiliser mode switch is second
from the bottom in this picture |
I tend to use position 1 most of the time for BIF and only switch
to 2 if I am doing an obvious pan .Having said that, in the heat
of battle there is often not time (or the presence of mind) to
flick the switch. I am sure I have taken plenty of sharp (and
unsharp!) pictures in both switch positions, so I would struggle
to make a firm recommendation here.
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