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Frequently Asked Questions About Binoculars:

  1. What do the numbers mean (e.g. 8x42)?
  2. What are coatings?
  3. What are multi-coated optics?
  4. What are fully multi-coated optics?
  5. Does the color of fully multi-coated optics matter?
  6. What are BK7 and BAK4?
  7. What is field of view (FOV)?
  8. How much magnification should I buy?
  9. Should I buy huge objective sizes?
  10. What "size" binoculars do I need to buy?
  11. How much should I spend on binoculars?
  12. What is the difference between porro- and roof-prism binoculars?
  13. If I wear eyeglasses, do I need to buy special binoculars?
  14. What is the exit pupil?
  15. What is eye relief?
  16. How do I clean my binoculars?
  17. How do I take my binoculars apart to clean them?
  18. What are zoom binoculars and are they any good?
  19. How do I use the diopter adjustment?
  20. Do I need to use a tripod or monopod?
  21. How do I mount my binoculars to a tripod?
  22. What if my question is not answered here?

What do the numbers mean (e.g. 8x42)?
The numbers stand for the magnification power and the objective size of the binoculars. The number before the "x" signifies the magnification power and informs you of how much closer or larger an image will appear compared to viewing with the naked eye. The number after the "x" stands for the size (usually in millimeters) of the objective lenses and is useful in understanding the amount of light-gathering ability of the optics. All else being equal, bigger front objectives mean distant images will appear clearer and brighter. Note: If the first number is actually two numbers separated by a hyphen or a slash, the binoculars are zooms or variable power.

What are coatings?
Coatings are layers of material added to glass surfaces to improve the performance of optics. They are primarily used to increase the amount of light that gets through the optics and into the eye. Without coatings, up to half of the light that enters the objective lens might never make it to the eye. Good coatings therefore mean a smaller objective can be used to gather the same amount of light and thus a smaller, lighter weight binocular can be used. Coatings also have other benefits such as improving contrast and reducing glare. You should be aware that not all coatings are the same. To carry the title of "coated", optics only have to have a single layer of magnesium fluoride on one lens. To be "fully coated", all lens have to be covered with at least one layer of coating.

What are multi-coated optics?
They are optics that have more than one layer of coatings applied to at least one lens.

What are fully multi-coated optics?
These are optics that have up to 25 layers of coatings applied to all lenses. This is considered top of the line.

Does the color of fully multi-coated optics matter?
No. Most manufactures have slightly different coatings which produce different color lenses. Some are green, others are purple, etc. However, do be aware that ruby colored lenses can be a sign of inferior optics.

What are BK7 and BAK4?
These are the type of glass used for the prisms. BK7 is borosilicate and BAK4 is barium crown. Generally BAK4 is more expensive and considered better because it provides sharper and brighter images than BK7. BAK4 also produces a perfectly round exit pupil, whereas BK7 typically has some distortion around the outer edges.

BK7 Versus BAK4 Graphic

What is Field-of-View (FOV)?
FOV stands for Field-of-View and it is the width of the image as seen through optics. This is often quoted as "width at distance" or in degrees. For example, 300ft@1000yrds would mean when the optics are focused at an object 1000 yards away, the width of the entire image as seen through the optics is 300 feet wide. If the number is given in degrees, it is either the angular FOV or the apparent FOV. For comparison purposes, multiply the angular FOV by 52.5 to get the standard FOV (e.g. 6 degrees X 52.5 = 315 [feet @ 1000 yards]). If the number given is larger than 15, it is probably the apparent FOV which can be divided by the magnification to get the angular FOV then multiplied by 52.5 to get the standard FOV. The wider the field of view, the easier it is to find and track objects (especially ones that are moving). This number is usually inversely proportional to magnification meaning that higher magnifications equal small FOVs.

Feild of View Graphic

How much magnification should I buy?
Most binoculars have a magnification in the 5x to 15x range. As discussed in the buying guide, bigger numbers are not always better because higher magnifications do have drawbacks. As with so many considerations, it mostly comes down to how you plan to use your binoculars (out hiking verses watching from a stationary location where a tripod can be used). A good general purpose pair of binoculars would be 7x35s or 8x42s since they should be light enough to carry hiking, have a wide enough FOV to see close objects and follow moving objects and yet powerful enough to see a fair amount of detail. For stationary viewing using a tripod, 10x50, 12x60, 15x75, or even 20x80 would be excellent choices. But remember, magnification by itself is just one part of the equation of getting that perfect viewing experience.

Should I buy huge objective sizes?
It depends on several factors such as how you will be using the binoculars. Larger objective sizes imply heavier optics. If you anticipate holding and carrying you optics for several hours, then the added weight should influence your decision. Alternatively, if you plan to do a lot of low light viewing such as dawn or dusk, the larger objectives will be advantageous since they have a higher light-gathering abililiy. Be aware that the size of the objectives has very little or no influence on the size of the field of view.

What "size" binoculars do I need to buy?
It depends on what you will be doing with them. For general birding, usually a good pair of 7x35 or 8x42 binoculars will be perfect. If you anticipate having to see over great distances or using your binoculars during dawn/dusk conditions, you will want to get a larger pair. Compact binoculars (with objectives less than 25mm) might seem like a good choice due to their light weight, but remember that the resulting image will usually not be as good as a standard-size pair of binoculars. It all depends on you...

How much should I spend on binoculars?
As much as you can reasonably afford. Binoculars are one of those things in life where you usually get what you pay for. There are some better values than others, but you really have to do your research. Of course, you probably don't want to spend so much that if your fancy new binoculars were to be dropped, lost, or otherwise irrepairably damaged, you would suffer financial and emotional pain. Buy the best that you can afford and as you progress, trade up to a better instriment. If you are a beginner, $100-$200 should get you started very nicely if you shop around. More advanced users may want to upgrade to something in the range of $250 to $750. Following that, name-brand, professional-level optics can easily cost $1,000+.

What is the difference between porro- and roof-prism binoculars?
Porro type binoculars have an angled light path and are the traditional looking binoculars. Roof prism binoculars have a "straight barrel" design and do not angle the light path. Contrary to what you may think, the roof prism type of binoculars typically cost more to produce than porros.

Roof vs Porro Design Diagram

If I wear eyeglasses, do I need to buy special binoculars?
Possibly, depending on why you wear glasses. If you wear glasses to correct far- or near-sightedness, you may not need to wear glasses when using binoculars because the focusing mechanism will allow for adjustment. However, if you wear glasses for other reasons, you should probably look for binoculars with a larger eye relief than standard binoculars. Eye relief in the range of 10mm to 20mm is considered larger then standard and these may be referred to as long eye relief or high eyepoint optics. You may also want to look for optics that have eyecups made out of a pliable materials such as rubber that can be rolled down/back over the ocular lenses to shorten the distance between the ocular lenses and the eyeglasses. You may also see designs that allow the eyecups to be twisted-down out of the way.

What is the exit pupil?
The exit pupil is the diameter of the light/image as it exits the ocular (smaller) lenses. Our pupils dilate with the changes in the brightness of our surroundings. Generally, a larger exit pupil is desirable when using optics in low-light settings (such as star-gazing) because the image will appear brighter and a smaller exit pupil is considered acceptable in brighter surroundings. If this number is not given, it can be determined by dividing objective size by magnification (e.g. 10x50 binoculars would be 50/10 = 5mm).

What is eye relief?
Also called the exit pupil distance (not to be confused with the exit pupil diameter mentioned above), this number is the optimum distance between the ocular lenses and our eyes. As a general rule of thumb, eye relief is inversely related to magnification (i.e. as magnification goes up, eye relief gets smaller). People who wear eyeglasses should pay extra attention to this specification because their eyeglasses increase the distance between the ocular lenses and the eye.

How do I clean my binoculars?
Start by blowing off any large debris and dust. Next, use a soft lent-free cloth (e.g. camera lens cloth) and lens cleaner or alcohol for the exterior glass and a soft cloth with warm water and possibly a mild cleaner for the outer metal, rubber, or plastic. Coatings can be relatively easy to scratch or damage, so be extra careful cleaning the lenses. Also, be sure to read the owners manual or consult the manufacturer for any additional instructions.

How do I take my binoculars apart to clean them?
You don't! In most cases you should not have to take you optics apart. Many are nitrogen-filled to keep the optics from fogging up. If you think the interior needs to be cleaned, contact the manufacturer or an authorized dealer for more information.

What are zoom binoculars and are they any good?
Zoom binoculars are optics with variable magnification. They can be used at a low power to find an object of interest and then be "zoomed" in on that object to see more detail. They work by changing the distance between the lenses. Zooms may not be right for all situations since images can become darker and blurry when set to a high magnification and the FOV is generally smaller than standard binoculars.

How do I use the diopter adjustment?
To set the diopter, first set it to zero and then cover the front lens of the side that has the diopter adjustment. Look through the binoculars and adjust the focus wheel until the image is as clear as possible. Then uncover the objective lens and cover the opposite one. Look through the binoculars and if the image is not clear, adjust the diopter until the image is clear for that eye.

Do I need to use a tripod or monopod?
In most cases, you will not need a tripod or monopod. However, if you plan to do most of your viewing from a stationary location, a tripod means you can use much larger objectives that are advantageous for low-light viewing. Also, very high-magnification binoculars typically require the use of a tripod. If you plan to be mobile and still want most the advantages of a tripod without all the weight, you may want to consider a monopod (single leg).

How do I mount my binoculars to a tripod?
A standard tripod will usually require an "L"-shaped adapter to use with binoculars.

What if my question is not answered here?
Try our binoculars buying guide and optics glossary. If it's not there, contact us.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
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