A request I received on many occasions during the last 20 years of my working life, let me explain [to newer birders] why this is the wrong question!
Firstly have a basic understanding of binoculars. There are two ‘styles: the original off-set, Porro prism ZCF [Zeiss Centre Focus] and the modern slim DCF [Dach/Roof Prism Centre Focus]. The top quality ZCFs can be brilliant to view through, but their close focus is poor and, because of the external focus bridge, unlikely to be waterproof. Also they are more prone to damage by knocks and bumps because of the simpler construction and therefore not so suited to the rough and tumble some birders inflict upon them! On the other hand, the construction of modern DCF’s with their internal focus mechanism will provide for waterproofing and, because the objective lenses are closer together, the near focus is better. Usually they will also survive minor knocks as the prism construction is more robust.
Don’t be confused by the numbers and letters that manufacturers use. It’s relatively simple. Let’s take the most popular birders specification to understand, 8x40 or 42. The first figure is how many times it magnifies, i.e 8x, therefore, a bird 100 metres away would appear to be 12.5 metres away. The second figure is the one that causes most confusion; this is the diameter in millimetres of the objective lens or the light gathering lens, the one pointing at the subject! Here I should also mention that there are a wide range and variety of ‘compact’ binoculars with equal magnification but with greatly reduced objective lenses. These are fine to use on a bright sunny day, but not the first choice for all weather condition birding. However if there is a young child in the family to be encouraged, this is what to start them with. The small size and lack of weight makes them ideal to handle.
In the past 50 years the change in optical performance of binoculars has been enormous, not only their resolving power but very importantly their light transmission. Even a quality German 8x56 or 10x70 binocular of 50 years ago would look ‘dim’ compared to a modern one, so that brings me to the second number. Divide the first figure [magnification] into the second and you will get the diameter of the all important exit pupil [the little white circle apparent if you hold the binocular away from your eye] and 7mm corresponds with the maximum performance of a young persons eye pupil. However 60 years ago lens coatings were rare to non existent and an uncoated lens lost 50% of its light transmission internally. Come to modern day optics where multi coating is the norm and the light loss can, depending on manufacturer and quality, be less than 2% so no longer do we have to carry enormous weighty lumps around our necks. At this point I should mention ED [Extra low Dispersion], apochromatic or fluorite glass used in some binoculars, but I won’t because the benefits are really only noticeable at larger [20x plus] magnifications, meaning we are In to telescope territory. Perhaps we will ‘enlarge’ upon this in a separate article at a later date.
Following the numbers on the binoculars are normally some letters, i.e. ‘B’ ‘WA’ ‘A’ ‘EL’ etc.... most are self explanatory, but let me just explain a couple:
B - is the German abbreviation for ‘spectacle wearer’ and means that the binocular is particularly designed to be used by those who do, and those who do not wear glasses. Most of the better quality manufacturers provide retractable eye cups, used in the down position if wearing specs and the up position if not. Stepping back some years this was never an option until Leica and Zeiss developed the style via fold down rubber eye cups back in the late 1960’s. Before then the actual image was formed totally on the rear optic, meaning that if you needed to wear glasses your eye was held away and your field of view considerably reduced. With a ‘B’ glass the image is projected back some 5 – 12mm away from the eye lens and also makes for more comfortable viewing.
A -signifies that the binocular is armoured - has a rubber protection around the body.
WP - waterproof, usually nitrogen purged.
PC - phase coatings – a special coating applied to the prisms to eliminate chromatic aberrations.
WA - wide angle. Take care as this can be a bit misleading since many people will also confuse the larger objective lens with producing a wider angle performing binocular. In fact you could not be more wrong as a more compact 8x32 will have a wider view than an equivalent quality 8x42! However the eye relief on an 8x32 is less than the 8x42 and likewise the light transmission, so it’s trade off time! The reason why 8x32s of quality, Swarovski or Leica for instance, have become so popular is that they are smaller and lighter to carry in the field and tend to have extreme close focussing. Bear in mind the previous comments regarding modern light transmissions and you will see where I’m coming from! Some manufacturers give the field of view as metres seen at a distance of 1000 metres, others as degrees. To compare degrees with the former, multiply the number by 17.5, for example 6 degrees equals a view of 105 metres at 1000 metres.
So what binocular do you buy for birdwatching? By far and away the most popular sales centre on the 8x42. The most you will comfortably hand hold for longish periods would be a 10x magnification [some swear they can hold more.....try it for a few hours and see!!] but at the end of the day remember the most important thing of all is the optical quality. It’s the reason why you can buy a binocular for 40 euros and yet a Swarovski equivalent would cost you 1400euros! It’s all, and totally all, to do with quality of optics and manufacture, nothing whatsoever to do with power. This is where the title of this article comes in. I used to keep a used pair of ‘zoom’ binoculars with me to show those who requested them, then I would offer a basic birders glass at a similar new price, no contest and it never was. But this brings me to perhaps the real point of this rambling article that I promised myself would not be too technical. Try before you buy. Not easy with the very limited availability of choice in Spain, but if you are in the market to invest in something decent it would pay to wait until you are back to the UK and attend a field sales event - retailers advertise them well in advance. This is the only way you can get the feel and see the optical difference plus expert help whilst watching what we all love. It doesn’t matter if you can’t afford a top marque, in these days of computer designed optics excellent quality can be obtained for comparatively modest prices; check out some adverts and to be honest if it’s ‘middle of the road’ you want look at the Opticron advert that appears in this very magazine. Without compromising too many trade secrets, if you look beyond the colour, trade name and outside presentation of most ‘middle of the road’ optics, they probably all originate in the same far east factory! However some have ‘brand’ names, some go through many wholesalers, some are sourced direct, so you can easily buy the same binocular but with a 100+euros difference in price, be warned!
If you buy from a reputable retailer they will help you ‘set’ the binocular up, but supposing you didn’t, here’s what to do. Firstly bend to shape so that you view one complete circle [unlike Hollywood films!], secondly set the right eye correction, this is unnecessary if you are wearing prescription glasses (correction will be zero). If not pick a fine detailed subject at about 100 metres distance, focus first with the left eye only using the main focus wheel [if you cannot close eyes individually block off right hand objective lens]. When happy with the sharpness switch to your right eye and close or block off left eye vision. Use the right eye correction adjustment until the same object is sharp and that’s it. Lock your setting if the binocular allows or if it’s a free moving scale note the setting. Check out the correction every few months, your eyes do change.
Your binocular will be supplied with a strap, fit it, and if a rain/dust/sand/biscuit guard came with it, fit that at same time, you need it trust me! The strap should hang around your neck at all times, accidents by being dropped are not covered under the long guarantees that manufacturers supply. The rainguard needs to be threaded on one side so that it drops away whilst the binocular is in use. If a rainguard isn’t supplied, please do buy one.
Care of your precious purchase. Too much cleaning is unnecessary - more harm is caused this way, in particular to the sensitive eye lenses. Using the rainguard will help, but should perspiration/sunlotion etc. be present on these lenses, the multi coating will show them as white blobs. To clean, first and foremost remove any trace of dust from the lenses either by blowing hard or using a soft brush and at the same time brush out the inside of the rainguard. Then, using a special multi-porous cloth [from optical retailers/opticians] gently ‘breathe’ on the optic and immediately wipe off. Try to avoid cleaning liquids they can cause problems over a period of time.
Derek Etherton, the Author of this article spent 40+ years in the photographic/optics trade including 18 years with Leica and 20 with ‘in focus’. His interest and eventual love of birds was encouraged by an enthusiastic teacher whilst at primary school. Now he’s happily retired watching birds in Spain and tending his fruit trees.
“My working life revolved around optics and in 1986 I was involved in the start of sales of binoculars and telescopes on bird reserves where I had many strange requests and my usual response to the title of this article was “Why, do you want to stand on them?” So aiming this article at the newer ranks of those joining our wonderful pastime please let me pass on some thoughts and hopefully some help. “.