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Binoculars & scopes buying guide

Choosing the right binoculars or scope for your needs and your budget can be difficult. Our buying guide will help you through the minefield of information and choices.

You can also get fantastic advice and try out different models at some of our retail stores.

Binoculars

A binocular is a fantastic tool for getting closer to nature. Which one you buy will involve a fair degree of personal preference rather than science, but here are some pointers to help you make a choice.

Magnification
In general, binoculars best suited to watching wildlife and birds do not have extremely high magnification. This is because big magnifications require a lot of light to work. Lots of light needs huge objective lenses, which would render the binocular impractical in terms of portability. In addition, high magnification makes it very hard to hold the image steady.
So, an 8x or 10x magnification is the best compromise between power and practicality. If you think of looking at an object with your naked eye as 1x, then an 8x binocular would make the image eight times bigger than your naked eye.
If you mostly birdwatch in open country and/or looking across large stretches of water, you may want the extra magnification of a 10x. However, if you mostly birdwatch in woodland, at fairly close quarters, and/or like to be out when the light may be poorer (dawn and dusk for example), you would be best to opt for an 8x model.

Brightness
When trying to identify wildlife, it is helpful to have as much light and colour as possible. A quick indication of brightness can be gained by dividing the diameter of the objective lens by the magnification. For example, an 8x42 binocular would have a brightness score of 5.25 (42 divided by 8), whereas a 10 x 25 would have a score of 2.5 (25 divided by 10). More expensive models also increase their brightness by adding sophisticated coatings to the lenses, and by using very expensive and highly engineered glass.

Weight And Size
If you do a lot of walking and already carry other gear with you, or if you have a medical condition, you may want to think about lightweight or compact models. However, it is worth noting that with a good neoprene strap, most people would not find any binocular particularly heavy in normal use. Very often, weight is associated with better quality lenses, and therefore a better quality of image. Some expensive models use light alloys in their body casing in order to decrease weight.
Most compact binoculars are only suitable for watching wildlife in very good light. This is because, in order to reduce their size and weight, the diameter of the objective lens will have been reduced substantially. A typical compact objective lens would be 25mm diameter, whereas a typical full-size model would have 42mm objective lenses.

Field Of View
Simply put, this is the ‘width’ you see when looking through binoculars.

Field of view

A wide field of view makes following moving objects easier – particularly important when watching birds. Expensive models will offer as sharp an image at the edges of this circle as at the centre. Spectacle wearers should look for twist-down eye-cups. These allow them to see the same size of circle as non-spectacle wearers, and are really handy when swapping quickly between those with and without spectacles. In general, 8x magnifications offer a better field of view than 10x.

Close Focus
If you like looking at dragonflies, butterflies and plants, you should make sure you go for a model that will focus down to 3m or less. Generally, an 8x magnification offers a better close focus than a 10x.

Price
As with anything else in life, there is an element of ‘you get what you pay for’ with binoculars. As the price increases, the quality of the materials used increases, the number of features increases, and guarantees are extended up to 30 years. Eventually, at the top end of the price range there is also the inevitable cache, reputation, or fashion element associated with all premium products. Whatever your budget, we will have something to suit you, so please ask one of our knowledgeable staff for assistance if you require it.

Telescopes

A telescope will give you more optical power than binoculars, but this extra power makes it less portable. To use it successfully, you need three basic elements: The main part of the telescope is called the body, and it gathers the image before transferring it to the eyepiece, which then magnifies the image. The tripod holds it all steady, so you can actually see the image clearly.

Body
The objective lens is probably the most important element of the body, and as a general rule, the bigger it is, the brighter the image will be. A small objective lens would typically be 50-60mm diameter, while a large one would be 70-100mm. If the body is filled with nitrogen gas, it will prevent it from fogging up. The more expensive models have sophisticated coatings on the lenses, which help to make the image as bright and free of distortion as possible. Most telescope bodies are angled these days. This makes them easier to use between people of differing heights, keeps the tripod lower and steadier, and makes tracking moving birds easier. It is the body which focuses the image, not the eyepiece.

Eyepiece
This magnifies the image gathered by the body, and is the part you look through. A telescope will not work without one! If it has a twist-down eye cup it will make it better for those wearing spectacles, because this allows them to see the full field of view. They come in two basic forms – fixed and zoom magnification. Fixed means you only get one power setting, and zoom means the power is variable. Zoom eyepieces, and fixed eyepieces of 40x and above, work best with large objective lenses, and in very good light. For general use, most people find 30x is more than adequate.

Tripod
A tripod is essential when using a telescope in order to keep the image steady and you would probably struggle to hold a telescope for a long time before it became unbearably heavy! There are many models and types, but they all do a similar job. In general, the more you spend on your telescope, the more you should spend on your tripod. You don’t want your lovely new equipment to crash to the ground because the tripod was too flimsy to support it! Some tripod legs are made from carbon fibre to reduce their weight, but this increases their price significantly. By combining these three elements, things out of reach of your binocular will suddenly become visible, and nearer objects can be viewed in stunning, close-up detail.

Digi-scoping

Digi-scoping has increased in popularity over the past few years, and technological advances and cheaper equipment have made it much more accessible to all. It is however a baffling subject for some people with a huge range of cameras, telescopes and adaptor combinations. The aim of this article is to give a brief background to digi-scoping and help answer some common questions.

What is digi-scoping?
In essence, it is taking a photo using a digital compact or digital SLR camera through a normal telescope (spotting scope). The telescope increases the magnification of the digital camera giving several times more magnification.
The amount of increased magnification is dependent on the eyepiece being used. The higher the magnification of the eyepiece, the greater the final magnification. It is also possible with this set-up to use the camera’s optical zoom to zoom in or out on the subject.

What do I need?
For digi-scoping you will need a camera (digital compact or digital SLR), a telescope, and in most cases an adaptor. Some people forego the use of an adaptor and hand-hold the camera to the telescopes lens. Adaptors however make life somewhat easier. With SLRs having a detachable lens, the lens is removed and replaced by a special camera adaptor marketed by the scope manufacturer and the appropriate T-2 ring.

Which digital compacts are best?
With so many digital compacts on the market it would be impossible to keep an up to date list of all the recommended cameras so here are a few basic facts to help you.

Zoom
This is one of the most important areas to take in to account when buying a camera for digi-scoping. It may seem obvious to go for cameras with a huge optical zoom of say 10x or more, but the results are usually very poor with such cameras because of an effect called vignetting.
A black circle round the edge of a photo is called vignetting; it is, in effect, the edge of the field of view seen through the eyepiece by the camera. To overcome this problem, the camera has to be zoomed in to narrow the field of view. With cameras that have a large zoom range i.e. 10x, this effect is greatly increased and may be so bad that it is not possible to overcome it at all. The general rule therefore is to choose a camera with a small zoom, 3-4x is best. This lower zoom also has the advantage of increasing the amount of light available to the camera’s sensor.

Megapixels
A digital photo is made up of lots of tiny dots or pixels, as they are known.
The more pixels in the picture the greater the detail. As you increase the number of megapixels in an image, the size to which it can be printed and still retain detail also increases. An image taken on a 4 mega pixel camera can be enlarged to produce an A3 print at best with A4 size being most suitable. An increase in megapixels also allows the image to be zoomed in to greater detail before the image becomes blurred or pixelated.
The increase in megapixels does come at a price, however, as the amount of data it takes to record the image also increases. An image from a 4 megapixel camera takes up less memory than the same image taken on a 8 megapixel camera. The time taken for an image to be recorded to the memory will depend on the speed of the memory card being used, the picture format and the memory buffer on the camera.
Many of the latest digital compact cameras have a megapixel rating of 10 or more and these will provide the greatest flexibility when it comes to editing and printing. With memory cards becoming cheaper and faster, the increased file sizes that an image takes up and the speed at which it is written to the memory card is of less concern.

Functions / Modes
Many of today’s cameras come with several preset modes such as snow, landscape, portrait, sport etc. and these settings change how the camera takes the picture and limit the amount of control you have over how the image is taken. With some digital compacts however, a range of manual controls/modes is included that allow the shutter speed, aperture, white balance, ISO etc to be adjusted manually by the user for the conditions and the results desired.
Whilst some cameras do not have the full range of modes such as shutter priority or aperture priority, they do include a manual mode that will enable settings such as ISO, sharpening, metering etc. to be controlled to a certain degree, these are not usually as sophisticated as the dedicated manual modes, but are better than the normal camera presets.

Adaptors
If you already own a telescope and do not wish to upgrade or change it, it’s probably worth checking if the scope manufacturer makes a digi-scoping adaptor specially for your scope. If they do make their own adaptor it is worth researching how the camera attaches to it. Some adaptors use a screw thread that attaches directly to the camera lens. If this is the case, it may influence the camera you buy i.e. finding one with a threaded lens.
Some manufacturers whilst not producing cameras with a threaded lens do make an adaptor that provides a thread to which an additional lens can be attached (Sony is one such manufacturer). These additional adaptors then make it possible to attach the camera to the threaded part of the telescope’s digiscoping adaptor.

What about Digital SLRs?
It is possible to use a digital SLR instead of a digital compact. Finding out if your SLR will attach to a telescope is easier as the only thing you need to ascertain is whether the telescope manufacturer makes an SLR adaptor for their range. If they do manufacture one it is just a case of buying the correct T-2 mount to attach the SLR body to the adaptor and telescope. T-2 mounts are usually available from the big SLR manufacturers such as Canon, Nikon, Pentax and Olympus.

Glossary of terms

OBJECTIVE LENS
The larger, or front lens. The Objective Lens Diameter is the size of the outer (front) lens in millimetres. A 7x35 binocular has a 35mm objective lens. This helps determine how much light enters the binocular, although image brightness still depends on the size of the exit pupil. Doubling the size of the Objectives quadruples the light gathering capacity of the binoculars; for example, a 7x50 binocular has twice the light gathering capability of a 7x35 binocular and four times the light gathering ability of a 7x25 binocular (all else remaining equal).

MAGNIFICATION
Also called “Power”, this number reflects how many times the image is magnified. For example, through a 10x binocular the image will appear 10 times larger than with an unaided eye, an 8x will magnify only 8 times. With 8x power, an object 800 feet away will appear as if it was only 100 feet away. Higher magnifications require a large objective lens in order to maintain adequate light transmission(see calculations under Exit Pupil). They also exaggerate and magnify hand tremor, so can be difficult to hold steady.

PRISM TYPE (ROOF or PORRO)
Images entering a binocular (or telescope) are both upside down and the wrong way round. Prisms are used (two each side) to convert the images so that we can see the images as they really are. Two types of prisms are common -- porro or roof. In general, porro prisms yield greater contrast, but many roof prisms have a phase-shift coating, which can provide similar contrast. Porro prisms are available in two standard types: BK-7 and BaK-4. The glass density of BaK-4 provides superior performance. Porro prisms set the objectives further apart and may offer superior stereo imaging. Roof prisms are lighter in weight, more compact, and often more expensive. The barrel appears to be a straight tube. BaK-4 and roof prisms have a perfectly round exit pupil, whereas BK-7 prisms show a grey area on the outer fringe of the circle.

BAK4 Glass Prism
A binocular prism design that produces a perfectly round exit pupil and ensures greater light-gathering power for clear images without any vignetting (where the image’s brightness is less at the edge compared to the centre).

COLLIMATION
How all the lenses and prisms line up inside the barrels. To work effectively, they need to be in just the right place and be parallel. High quality mechanical construction will ensure that the lenses and prism blocks maintain their correct alignment and provide years of comfortable viewing without headaches or eyestrain. This is what needs repairing when binoculars have been ‘knocked out of alignment’.

EXIT PUPIL
Measured in mm, this is the diameter of the beam of light leaving the binocular eyepiece, and determines how much light the eyes receive. Larger exit pupils provide brighter images. To calculate Exit Pupil, divide the objective size by the power. For example, the exit pupil of a 7x42 binocular is 42 divided by 7, or 6mm. Since the pupil of the human eye can shrink to a diameter of 2mm to 4mm on a sunny day, this specification is of greater importance for use in low light.

EYE RELIEF
Measured in mm, it is the actual distance, your eyes could be from the surface of the eyepiece, and still see the full image. Long Eye Relief allows users who wear glasses, where the eye is further away from the eyepiece, to see the entire field of view. Can be accommodated by twist down or fold down eyecups.

FIELD OF VIEW
Is the width of the area (in degrees) that can be seen at a given distance (usually measured at 1000 metres). Also explained as the size of the circle of image you see when looking through the binocular. A large field of view permits you to see a large area at one time, and enables you to follow a moving subject with ease. Generally, the higher the magnification the smaller the field of view.

Field of view

DEPTH OF FIELD
This refers to how much of the view is in focus at any one time. A good depth of field will mean less re-focussing between objects at different distances away. This can help to prevent eyestrain, and makes following moving objects easier, as well as making the binocular always appear ‘ready’ for use. Higher magnification decreases depth of field.

Depth of field

CLOSE FOCUS
For those interested in insects or plants, close focus is very useful. It would usually refer to distances less than 3 metres. The downside of close focus is that depth of field can be compromised to achieve it.

DIOPTRE ADJUSTMENT
As most people have a difference in the sight of each eye, most binoculars have a mechanism that helps allow for this - effectively creating individual focus for each eye. Older models have the dioptre incorporated into one eyepiece, but equipment that is more modern will have it separate from there so it can be adjusted and ‘locked’.