This is only a preview of the March 2003 issue of Silicon Chip. You can view 27 of the 96 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "LED Lighting For Your Car":
Items relevant to "The PortaPAL Public Address System; Pt.2":
Articles in this series:
Purchase a printed copy of this issue for $10.00. |
product review
Canon’s
image stabilised
binoculars
W
hether you like to watch whales, birds or sport,
a pair of binoculars is a great accessory. How
ever, they do have disadvantages. Most
binoculars are not light and the longer you use them, the
more tired you become.
And the more tired you become, the harder it is to hold
them steady and this problem is worse if you are using
magnification of x10 or more.
The only practical solution to both of these related
problems is to use a tripod. This relieves the
strain on your arms and holds the
binoculars absolutely steady
but most people would
find a tripod just another piece of gear that
they don’t want to
carry.
Canon’s solution to the problem is to produce binoculars
with inbuilt image stabilisation.
They compensate
for the inevitable
“shakes” you get
when using binoculars
and they are much more
pleasant to use.
We reviewed two of the Canon
range: the 15x50IS model which has
50mm objective lenses and x15 magnification and the 10x30IS which has
30mm lenses and x10 magnification.
Cutting straight to the chase, the
x15 model is the one of most interest,
since that degree of magnification
is almost impossible to use without
having a tripod. In fact, unless you are
experienced in using binoculars, it is
difficult to imagine how difficult such a seemingly modest
degree of magnification is.
76 Silicon Chip
This cutaway diagram shows the disposition of the major
components in the Canon image stabilised binoculars. Note
the compact Porro prisms which erect the inverted image
for normal viewing.
www.siliconchip.com.au
by Leo Simpson
The Canon 10x30IS binoculars (above) are much more
compact and half the weight of the higher power 15x50IS
model (left) but use the same image stabilisation system.
In effect, even
if you are pretty steady
on your feet, and
you brace yourself against a wall, table or whatever, you
will find the object you are looking at shakes around so
much that you quickly get frustrated with the attempt – it
is that hard.
But switch on the Image Stabilisation and all of a sudden the images snap into a rock steady condition and you
can view in much more comfort. You can pan around
and even view from a boat or moving car. In short, Image
Stabilisation makes viewing at x15 magnification entirely
practical and satisfying.
It is even more effective on the smaller x10 binoculars
and their much lighter mass means that you can view for
much longer before arm fatigue gets you.
flat glass connected by flexible bellows which can expand
and contract as required. The bellows are filled with a
silicone-based oil which has a high refractive index (presumably the same as that of the glass plates). One glass is
driven to compensate for pitch movement while the other
is driven to compensate for yaw movement.
The drive system is a yoke (coil) and magnet system for
both X and Y axes with Hall Effect sensors for feedback
while the movement sensing is done by accelerometers.
While there is a separate vari-angle prism for the left and
right eye optical paths, both prisms are linked together and
driven by the X and Y axes yoke/magnet systems.
We include a cut-away diagram showing the major internal features of the Canon binoculars. Notice that they
do include Porro prisms to erect the image but the overall
So how do they work?
shape of the Canons might suggest that they are using the
more compact roof prism construction. Another diagram
Broadly speaking, there are two methods of image
shows more detail of the image stabilising mechanism,
stabilisation. The first is widely used in camcorders and
including the yoke and magnet drive systems.
involves using only part of the image produced by the CCD
By way of explanation, all binoculars (except opera glasssensor. In effect, the internal computer looks for the steady
es) require prisms to erect the inverted virtual image for
part of the image from the sensor and continually “edits
normal viewing. Most
out” the shaking borders,
conventional binoculeaving a much steadier cenSpecifications
lars use Porro prisms
tral image to be displayed as
15 x 50
10 x 30
which give a Z-path
the video output.
Magnification
15
10
to the light beams –
The second method, used
this accounts for the
in these Canon binoculars
Objective lens diameter
50mm
30mm
big offset between
and in some high-priced
Real field of view
4.5°
6°
the objective lenses
telephoto lenses, is to staField of view at 1000m
79m
105m
and the eye-pieces. In
bilise the image itself by
binoculars with roof
Focus
range
6m
to
infinity
4m-infinity
passing it through a prism
prisms, the light travwhich can be continually
Exit pupil diameter
3.3mm
3mm
els in a straight line
moved to compensate for
Eye relief
15mm
14.5mm
and therefore they
the shaking of the binoculars
Dimensions
152
x
193
x
81mm
127
x
150
x
70mm
are generally more
themselves.
compact.
Canon uses what they call
Weight (excl batteries)
1200g
630g
The Canon Image
a “vari-angle prism” which
Battery life (alkaline)
2.5 hours
4 hours
Stabilisation are obconsists of two pieces of
www.siliconchip.com.au
March 2003 77
The drive system for the vari-angle
prisms uses yoke coils and magnets
to compensate for pitch and yaw of
the binocular body. Motion sensing is
performed by solid-state accelerometers.
viously using a different arrangement of Porro prisms
because the two objective lenses are solidly fixed within
the binocular body while the two eye-pieces can be rotated
to change the inter-ocular distance. The result is that the
Canons are quite a bit more compact than conventional
roof prism binoculars.
Another interesting feature is the inclusion of a doublet
field flattener in the eye-piece lenses. This reduces the
curvature of the field and avoids the usual distortion at
the periphery of the image. It also gives long “eye relief”
which means that people with glasses can comfortably use
the binoculars.
The Canon 15x50IS binoculars are powered by two
AA cells which last for up to 2.5 hours continuous use
for alkalines or Nicad cells (at 25°C). If you use lithium
batteries, this can be extended out to 8 hours continuous
use. Alkaline battery life for the smaller 10x30IS model
is 4 hours.
Using them
Referring to the Canon 15x50IS model first, they are
comfortable to hold and easy to focus. However, people
with small hands will find them difficult to grasp, even
though they do have a non-slip rubber skin. And at over
1kg, most users will find that they are tiring to use for more
than a few minutes at a time. They do have a tripod socket,
so a monopod would be very worthwhile if you need to
use them for extended periods.
78 Silicon Chip
Since I am interested in astronomy, I was keen to check
how they would perform when viewing planets and stars.
Unless you have a tripod/chair setup, the common way to
use binoculars when viewing the sky is to lie down on the
ground or on a reclining chair. But even this method can
be very tiring and the star images tend to dance about all
over the place after a few minutes.
With the Canon 15x50IS, it is a much more satisfying
experience. Stars and planets can be held steady and you
can easily achieve optimum focus. There is some flare and
signs of chromatic aberration on star images but generally
this is at a low level; after all, they are not really intended
for astronomical use.
By contrast with the Canon 15x50IS, the 10x30IS are
much more comfortable to grasp and hold, due to their
much smaller size and weight (630g). However, with a
magnification of x10 and good optics, they are very usable
and compare very well with conventional 10x50 binoculars.
We like them a lot.
Pricing
This is great technology but there is no getting away from
the fact that these Canon Image Stabilisation binoculars are
expensive. The recommended retail price for the 15x50IS
model is $2499 including GST while the 10x30IS sells for
$1249 including GST.
For further information, contact Canon at 1800 816 001
SC
or www.canon.com.au
www.siliconchip.com.au
|