Binoculars – Why I bought the Nikon Prostaff P7 8×42

a pair of binoculars


Binoculars are devices created to enhance our outdoor experiences. They are used for bird watching, hunting, hiking, astronomy, watching sports events and concerts from a distance, and whale-watching. Binoculars are great; however, they are not designed equally.
Several factors influence your choice of the best binoculars, especially what you want to see. Therefore, it might get confusing when deciding which binoculars to buy. This article will guide you on how to choose binoculars suited to your needs.


What do the numbers on binoculars mean

The model numbers present on binoculars are specifications that describe their strength (magnification power) and size (objective lens diameter in millimetres). For example, a pair of binoculars with the specifications of 8×42 has a magnification power of 8 and an objective lens size of 42mm.

Objective Lens

The objective lens is the larger one at the front of the binoculars and determines the binoculars’ overall specification. Objective lens size also determines how much light enters the binoculars and is transmitted to your eye. A larger objective lens means more light can get into the binoculars, thus giving you a brighter image.
Larger objective lenses also make the binoculars bigger and heavier. Therefore, in your search for the right binoculars, find a balance between brightness and portability.


The magnification power explains how large the binoculars make a distant object look. For example, binoculars with specifications of 8×42 will provide eight times magnification, which makes objects, animals, etc., look eight times closer.

Higher magnification binoculars always sound good, but they come with a few issues. More magnification generally leads to less stability. Also, the farther the object’s distance, the shakier the image becomes when viewing it.

Holding a small object in view is more challenging if you look at it from a distance. At larger magnifications, any shaking of the hand becomes much more pronounced, making the image appear blurry. However, as you continue using the binoculars, you will adapt and figure out how to reduce hand twitching.

The other issue with higher magnifications is a narrower field of view (FOV). While unlikely, you’ll find a bird or other objects that won’t always fit a 12x pair of binoculars’ field of view. Also, getting that bird/object framed in your binoculars is tricky for beginners.

Seeing your target with the naked eye and then getting it within the frame of your binoculars is a skill on its own. However, you get better and better with practice.

Rubber eyecups

If you wear glasses for normal vision you will find that rubber eyecups will make using binoculars both more comfortable and your image will benefit from more contrast as stray light is dramatically reduced.

Eye Relief

Ideally, the exit pupil will land at your point of focus, or ‘eyepoint’. Without wearing glasses this eyepoint is the lens of your eye; however, if you wear glasses this eyepoint is moved forward to the lens of your glasses. Adjustable eye relief means that the eyecup can be moved (away from the body for use without glasses, and vice-versa).

Neck strap

It is surprising how heavy good quality binoculars can become after walking around for a while.

If using small binoculars it’s relatively easy to slip them into a large pocket or bag, but for larger binoculars a neck strap is essential, and here is where not to scrimp. If they’re going to become uncomfortable you will soon stop taking them out with you.

Recommended Binoculars for Specific Purposes

Binoculars for Birdwatching

Birds are small creatures and may be hard to see sometimes. Therefore, use binoculars with larger lens sizes and those that do well in low light conditions. They should also be lightweight, so your arms don’t get tired. The recommended binoculars for birding are the 8×42 binoculars.

Binoculars for Hunting

The recommended options for hunting in forested areas are 7×18 to 10×56. For long-range shooting, you should consider powerful binoculars like 12×40 and 16×50. However, you’ll need a tripod to stabilize the binoculars, as the image will be shaky in a standing position.

Binoculars for Stargazing

The perfect binoculars for stargazing will have a balance of low-light gathering capabilities and magnification. If you have a tripod stand, you might opt for high magnification binoculars with big lenses, say 20×80, though, as this is a nighttime activity the exit pupil (80/20=4) of 4mm is too small to provide a bright image. A 10×50 will be your next best bet if you don’t have a tripod as this provides a 5mm (50/10=5) exit pupil. Human eyes will, typically, have a pupil diameter of around 7mm to 9mm when out looking at the night sky, for this reason, 12×80 is more appropriate as the exit pupil is near 7mm (80/12=6.7) in diameter.

Binoculars for Boating and Mariners

A large magnification is not advised since you’re on the water. The most commonly used magnifications are 7×40 to 7×50 as these provide ample magnification combined with being relatively easy to hold the subject steady in the field of view. Clearly, waterproofing is important and the temperatures and environment would suggest nitrogen-purged models. Of course, a good neck strap is recommended.

Why the Nikon Prostaff P7 8×42 Binoculars?

The first thing to do was to settle on my requirements because, having looked at and owned a lot of binoculars, I now wanted a pair for general use.

My criteria were simple:

  • magnification: x7 or x8
  • Objective lens: minimum 40mm, maximum 50mm
  • Exit pupil: around 5mm because I will use the binoculars in a range of light levels, so something between 2mm and 8mm (bright light and low light)
  • Weight: Less than 750g
  • Waterproof: Must be able to withstand heavy rain for at least 10 minutes
  • Nitrogen purged: This was a must as the conditions I will use the binoculars will vary
  • Rubber eyecups: Yes, because I need to wear glasses at times
  • Eye-relief: Must be adjustable
  • Dioptre adjustable: Yes, for when I’m not wearing my glasses, and when I am.
  • Tripod mountable: Would be nice, but not essential
  • Price: Less than £250

With the above in mind, I went shopping!

I put a list of brands that I trusted together, including Swarovski, Olympus, Pentax and Nikon, and price immediately knocked out the Swarovski brand.

It was then a case of comparing the specifications against my list of criteria, above and only one pair met all of them and felt nice in the hand: The Nikon Prostaff P7 8×42 Binocular, with one bug-bear in the rear lens cap… It just falls off. Looking online, this seems to be a fairly common complaint but I figured that when not in use they would be in the supplied case.


(Item No.BAA840SA)
Magnification (x) 8
Objective diameter (mm) 42
Angular field of view (Real/degree) 6.8
Angular field of view (Apparent/degree) 50.8
Field of view at 1,000 m (m) 119
Exit pupil (mm) 5.3
Relative brightness 28.1
Eye relief (mm) 19.5
Close focusing distance (m) 4
Length (mm) 167
Width (mm) 129
Depth (mm) 55
Weight (g) 650
Interpupillary distance adjustment (mm) 56-72
Prism Type Roof


Nikon PROSTAFF 7S 8x42 Binoculars

Nikon Prostaff P7 8×42

Nikon PROSTAFF 7S 8x42 Binoculars<br />
adjustable Eye Relief

Adjustable Eye Relief

Final Thoughts

I spent a long time making my decision, and I am very happy with my binoculars. If you are interested in the same, they are availalbe from Amazon here:

Further Suggested Reading

As usual, Wikipedia can offer some in-depth detail:

Olympus made the first quality binoculars I ever owned and their site has interesting information: Olympus help page


    • Price/performance ratio
    • Waterproof
    • Great eye relief
    • Bright image


    • Eyepiece cover – just annoying
    • Sensitive to positioning when adjusting width


What is better 10x42 or 12x50?

This is a typical question. The true answer is “it depends”. Magnification and objective lens size governs the brightness of the image; however, in the case of 10×42 vs 12×50, brightness (exit-pupil) is practically the same but the 12×50 carries a lot more glass and, therefore, weight and will be more difficult to hold steady; however, the lighter and more stable 10×42 has lower magnification.

What does Exit Pupil in binocular specifications mean?

Exit Pupil refers to the diameter of maximum brightness visible from the binocular eyepiece. It’s a direct relationship between the diameter of the binocular’s objective lens and its magnification. Essentially, the higher the magnification the larger the objective needs to be to retain a bright image.

This is the reason that there are ‘classic’ ratios such as 10×50, 7×50, 8×30, 10×42, etc. They provide exit pupils of 5mm, 7.14mm, 3.75mm, and 4.2mm respectively. You can see that the exit pupil of the 10×50 is significantly smaller than the 7×50 in the examples above. The key to a bright image is to match the exit pupil to the pupil in your eyes, which expands in low light and contracts in bright light. The typical range of the human pupil is between 2mm and 8mm diameter.

Why are some binoculars filled with nitrogen?

The space between binocular lens elements is often filled with nitrogen gas to eliminate internal fogging that would otherwise arise from air-filled units when the binoculars are moved from warm to cold environments ie from inside a jacket to outside.

In addition to eliminating fogging, nitrogen-purged binoculars prevent the growth of any fungus on the lens elements as all oxygen is removed during the filling process. Nitrogen purging is also an indicator of the waterproof ability of the binoculars.

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