Bird Watching Binoculars

What's important to you may not be important to someone else.

We all know that trying to spot a warbler flitting around in the conifers with binoculars is a bit more challenging than focusing on an elephant on an African safari! Needless to say, birders need more in a binocular than the average elephant-watcher. Having a good pair of binoculars may make the difference between identifying that life bird or not.

So what is a good pair of bird watching binoculars? There are a lot of features these days on binoculars that need to be considered when making a purchase.

What do all the numbers mean? Should I choose porro or roof prism? Do I need my bins to be nitrogen-purged? Fully multi-coated? What does it all mean?

Lets start with some of the basics and what each means to ultimately choosing the best bird watching binoculars.

Magnification

Binoculars are categorized by a set of numbers such as: 7x35, 8x42, 10x50, etc. The first number is the magnification or how many times closer an object will appear than without magnification. So with the 7x35s, objects will appear 7 times closer, 10x50s, 10 times closer. For example, if you have an 8 power binocular and you are 80 feet away, the image will appear as though it is 10 feet away.

Most birders will choose a binocular with a magnification of 7, 8 or 10. But why wouldn't you want the highest magnification you can get Obviously, higher magnification will give you a closer & more detailed look. But there are some drawbacks.

Lower power bins will allow you to see more because of a wider field of view (FOV discussed later). Basically, the higher the magnification, the narrower the field of view. You can see more of what you looking at through 7x than 10x. You'll also have a better chance of spotting a bird & following it as it jumps around in the trees with 7x than 10x. Additionally, if you are watching flocks of birds, you will see more individuals in a 7x than 10x.

Comparing 7x40 with 10x40s (same objective lens size), the 7x will also give you a brighter image (image brightness decreases with higher magnifications). This is especially helpful in low light conditions, i.e. owl watching, in dense forests, and at dusk & dawn.

Higher Magnification Disadvantages:

• Smaller field of view
• Less light (bird image will be not be as bright)
• Have to hold more steady - higher magnification exaggerates shaking when hand-held
• Heavier
• More difficult to focus on close objects
• Takes more time to focus - more focus wheel rotations

The above taken into consideration, you still may prefer 10x over 7x or even 8x, especially if you plan to use your bird watching binoculars mostly for:

• Distant bird watching such as shorebirds or raptors
• Viewing in wide-open situations
• Viewing birds not as active such as waterfowl

If you require anything above 10x, you should consider using spotting scopes because binoculars above that magnification power will be too difficult to hold steady.

If you plan on using one pair of binoculars for all your birding, 8x are a good compromise and is the choice of many birders. When it comes down to it, a 10x binocular, although offering slightly more detail, will not make the difference between you being able to identify a bird or not. So for the sake of price & comfort, you may want to choose a pair of 8x or 7x. It will provide you with the best value for your $ as well. You should stay away from low-priced(<$100) 10x bins. You will be better off purchasing a $50 pair of 8x because typically flaws increase as magnification increases in cheaper models. 7x and 8x are better especially for beginners who may need a larger field of view to spot and follow active birds.

Decide what's important to you...more detail or brightness of image Heavy or lightweight Do you have shaky hands Is it easy for you to spot birds through binoculars Do you need a broad field of vision or small If you can, borrow different kinds of binoculars to see what works best for you.

Objective Lens Diameter

The second number on the binoculars is the the diameter in millimeters of the objective lens (front, big, fat lens on far side). So 7x35s has a lens size of 35mm, 8x42, 42mm. Why does it matter

This is where light enters your binoculars. So the bigger the lens, the greater its light gathering capacity & the brighter your bird will be - the better detailed field marks will be able to see & colors will be more brilliant.

So why not have the biggest lens Because bigger means bulkier & heavier. A 50mm lens is as big & heavy as you would want to go. Fine if you're sitting on your backyard lounger, bad for a week-long backpacking trip. Weight of binoculars is discussed in more detail later.

When I was choosing my first pair of bird watching binoculars many years ago, I was told to get binoculars with an objective lens size 5 times greater than the magnification.

So if you are choosing 8x bins, the objective lens size should be at least 40 (8x40), 10x bins should be 10x50, etc. However, optic quality has increased greatly over the years and now you don't necessarily have to follow that rule, at least for binoculars priced $200 and up.

As a general guideline, choose a lens size between 30-50mm. Compact binoculars usually will have lens sizes below 30mm. Yes, they will be lightweight, but you lose light and handling comfort. So don't choose compact bins if it is going to be your only pair. The popular sizes for bird watching binoculars are 8x40s or 8x42s after comparing brightness, field of view, and weight with smaller & bigger binoculars. 30mm is the smallest any birder would want to go.

If you often use your bird watching binoculars for viewing owls and other birds in low light conditions (dense, dark woods or at dusk & dawn), then consider a bigger objectives lens. More light gathering means more detail when the light level drops, and therefore, more quality birding time when the birds are active.

And keep this in mind too, a high quality 40mm lens will give you a better image overall, than a cheap 50mm lens.

Increasing Objective Lens Size =

• more light
• more weight
• more expense

Bird Watching Binoculars

Exit Pupil

The exit pupil is the diameter of light in millimeters visible through the eyepiece. It is determined by dividing the objective lens diameter by the magnifying power. So a pair of 10x50s would have an exit pupil size of 5mm (50/10 = 5). 8x32s would have an exit pupil size of 4mm (32/8 = 4)

You can see this beam of light when you hold up your binoculars (eyepieces towards you). It appears as a tiny circle of light in each eyepiece. The circle of light is the magnified image as it exits the binoculars and enters your eye. The bigger the diameter, the better youll see in dim light, up to the maximum diameter of the human pupil itself, generally between 4mm to 7mm, depending on age and available light.

Obviously then, the larger the exit pupil, the more light gathering capacity, and the brighter your bird image will be. If the exit pupil size is near the same size of our pupil, it will be more difficult to find images. For example, in bright light when our pupils are contracted to 2-3mm, those compact 8x21 bins (exit pupil = 2.6) are going to be difficult to use because our eyes are going to have to be centered exactly over the exit pupil to find our bird. Trying to follow an arctic tern on a rocky boat with a pair of compacts will have you barking at the buoys in no time! The image will also appear darker and not as clear.

For general purpose birding, choose a pair of bird watching binoculars with an exit pupil size of at least 4mm. If you do most of your birding in shaded conditions (thick forests), dim light (owling) or on boats, choose 5mm or more.

Bird Watching Binoculars

Prism Design

There are two types of prism systems, porro & roof:

Porro
Porro prism binoculars have a z-shaped optical path where the objective lenses are offset from the eyepieces, resulting in a wider set of binoculars.

Roof
In roof prism binoculars, the prisms overlap closely and the objective lenses are approximately in line with the eyepieces. The result is a slim, streamlined shape.

Because of the pricier technology required, roof prisms are more expensive than porro's. You can get an excellent pair of porro prism bird watching binoculars priced around $250. To get the equivalent optic quality in a pair of roof prism bird watching binoculars, you would have to pay around $400 and up. So if your on a budget, porro prism may be your best option. Remember though, that because porro's are not as rugged and durable as roof's, you may be better off in the long run with a roof prism if you can afford it.

Comparing Porro & Roof Prism Bird Watching Binocular Designs

Porro	Roof
Big & bulky	Slim & stream-lined
Heavy	Lightweight
External focus: o-ring seals' degrade & allow dirt & water to penetrate interior	Internal focus - easier to waterproof & seal
Wider field of view	Prisms overlap closely, smaller field of view
Wider offset lenses provide greater depth perception	Straight inline barrels decrease depth perception
More light gathering capacity = brighter	Can be as bright as porro with proper lens coating (PC phase corrected coating) = $$
2 offset prisms mounted separately - more susceptible to alignment problems if dropped - weaker design	2 separate prisms cemented together as a single interior mount - stronger, more durable design
You can get a better quality binocular for less $$	Costs more for comparable porro quality

Close Focus

Close focus is the shortest distance at which the binocular is capable of providing a sharply focused image of an object. As a general rule, as magnification increases, the minimum close focal distance also increases. So yet another trade-off for you to consider. More magnification or better close focus

Especially of interest to birders because there will be times when you will want to see the detail of a bird less than 15 or even 10 feet away. Therefore, a good birding binocular should have a minimum close focus of 15 feet, 10 feet would be better. If you like to view other creatures up close such as butterflies, reptiles, etc. close focus is also an advantage.

Bird Watching Binoculars

Ease of Focusing

A good pair of bird watching binoculars will allow you to get a quick & sharp focus of your bird. This is important in because many birds are constantly moving around and you will need to be able to focus quickly. A good focus mechanism will focus from close to far with one full revolution of the dial or less. You don't want to have to turn the knob too many times in order to bring a bird into focus.

And make sure you get a pair of binoculars with a central focus that you can comfortably turn with your index finger. It should turn smoothly, without much effort. You will find that most birding binoculars do have central focus. Some models of binoculars have individual focus eyepieces which must be adjusted when looking at birds closer than about 30 feet, which is awkward and time consuming for bird watching.

Again, you get what you pay for so you'll find that more expensive bird watching binoculars have finer-tuned focus mechanisms. Again, try out a bunch out & see what's comfortable for you.

Now go to Birding Binoculars Part II of our choosing bird watching binoculars review.Or you may want to compare some of the best binoculars for bird watching as reviewed by the Cornell Lab of Ornithology.

Our favorite binoculars - click for review and best price online - Nikon Monarch ATB 8x42 Binoculars

For a great birding vacation to use your new bird watching binoculars go to:

Coastal Revelations Vancouver Island Bird Watching Tours - You get customized bird watching tours in central Vancouver Island, British Columbia, Canada. Discover the birds of the ancient rainforests, mountain meadows, marshes and sea shore with a biologist.