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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