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Which is better? Well, they
both have their advantages.
With optical IS there’s an argument
that it’s better because it’s tuned to
individual lenses. Plus, with longer
lenses, larger movements are
required in stabilising movement,
and these are easier to achieve in a
lens than in the body, because in
theory the lens barrel can be
widened. Optical IS also helps with
low-light AF on DSLRs, because the
light is stabilised when it reaches
the AF sensor.
The downsides are that IS-
equipped lenses tend to be larger
and cost more, and can usually only
correct for pitch and yaw
movements of the camera. It’s also
claimed that optical IS can degrade
the bokeh in defocused areas as the
light is shifted, but the differences
are negligible. You may also hear
sound from the optical IS unit,
though the same can be said for
some sensor shift technologies, too.
With mechanical IS, the biggest
advantage is that the system should
work with any lens you mount on
the camera, so it’s a one-time cost.
You can even fit legacy optics, though
you may need to set the focal length
manually via a menu if the lens
doesn’t communicate with the body
automatically. Modern mechanical
sensor shift systems can also stabilise
across more axes than an optical
system, so instead of just pitch and
yaw movements these ‘five axis’
systems will also correct for roll
around the lens axis, which becomes
problematic during long exposures,
along with vertical and horizontal
motion that causes blur with close-up
shooting. As a by-product of using
in-camera stabilisation, non-IS lenses
are cheaper and smaller, and there’s
less to go wrong with them!
As for the downsides of
mechanical or sensor-shift IS, the
main thing is that this method can
be less effective when using very
long lenses, because the sensor needs
to move more to compensate, and is
physically restricted in doing so by
the camera body. IBIS also increases
the camera’s size and cost.What about dual IS systems?
Increasingly, mirrorless camera
systems now use a mix of the two
technologies, with a mechanical
sensor-shift system in the camera as
well as optical IS in some – but not
all – lenses. For instance, Nikon’s Z
70-200mm f/2.8 S lens still has a VR
mode, even though the full-frame
Z-series cameras have IBIS. If you use
first-party IS lenses with your chosen
body you can expect them to work
together, and this best-of-both-
worlds approach increases the
amount of stabilisation offered by
taking the best of both technologies.What are the limitations of IS?
Photographers relying on IS for
increased sharpness in low-light
conditions are faced with one main
challenge: subject movement.Anything moving in the scene will
be blurred if the shutter speed isn’t
fast enough to freeze it. You can see
this in street scenes with blurred
pedestrians and cars, and even use it
for creative effect. Ultimately, it’s up
to you to get the shutter speed right
for the subject and IS will still be a
benefit in the wider scene.
IS should also be turned off when
shooting from a tripod. That’s not
necessarily because it will cause
problems, though. While older
systems could suffer from what’s
called a ‘feedback loop’, where they
detected their own vibrations and
softened the image, modern IS
technology should detect a lack of
movement. But switching IS off
saves battery power, which can be anAbove: Stabilising
the sensor or lens
also lets you use
smaller apertures
or intentionally
slow the shutter
as when
overexposing in
mist
Nikon D810, 24-70mm,
1/4sec at f/14, ISO 400Below: Today’s
sensor-shift or
IBIS systems
should allow five
axes of correction