Tag Archives: Pentax Binocular

Understanding Binoculars

I have been asked many times over the years what kind of binoculars I would recommend to new bird watchers, or for those looking to replace an older pair, what to look for when choosing a new pair of binoculars.

In trying to answer people you need to try and understand what their needs are first. The answer might seem obvious at first in that they need the new pair for bird watching. Of course there are many different usage scenarios when bird watching.

What if the person is a guide that uses their binoculars mainly in low light forest conditions or they bird mainly in open areas with large distances. This is where understanding the numbers associated with a pair of binoculars becomes important.

The first two main numbers you need to understand are the magnification and the objective lens diameter. So if you see a pair being advertised as 10X50 then your magnification is 10X and the front objective diameter is 50mm.


Magnification is pretty straight forward and is simply the amount by which distant objects are enlarged by the optical properties of the glass lenses. The higher the magnification number the more the objects are enlarged so 10X provides greater magnification than 8X and so on.

The Objective Lens Diameter relates to the size of the from glass element. In basic terms the larger the font lens the more light that can be transmitted through the lenses. Therefore objects appear brighter through the binoculars when viewed through a 10X50 binocular as opposed to a 10X43 or 10X30.

There are a lot more factors that can affect a buying decision but the above two are the most basic. When it comes to choosing a pair for birding, you really need to look at what kind of needs you have and where you do your most birding.

Open brightly lit areas where your subject is far off is very different to birding in a dimly lit forest where you might need to focus very close to get a good view of the bird. In the first case a 10X50 or even a 12X60 pair that does not focus close is perfect. However if you try and transfer that to a forest where your bird is potentially close and in a dimly lit area, then an 8X43 is much more suitable.

I personally have always chosen a 10X50 so I get middle ground when it comes to magnification but still let the most amount of light possible in through the binocular. This is because I can find myself birding in just about all habitat types.

As for the brand, there are many choices out there and of course a large price range. As is the rule with most things you get what you pay for. The Leica, Zeiss, Swarovskis of this world command premium prices and the optics are outstanding. However you can pay considerably less and still get to 90% of what these top brands offer. Both Pentax and Nikon have very very good optics in their binoculars at a vastly cheaper price.

Always do your research. Go online to the various stores, have a look around, then go into a store and try them out. Have a look through the binoculars and see how you find them. Try the different magnifications and lens diameters and see what feels comfortable. Beware of very cheap binoculars where you start to see purple fringing. This is where quality coatings on the glass come into play. Do the lenses line up or do you feel they are pulling your vision? Be very careful of this as you will be spending a lot of time looking through them.

When you look through them are you looking through a small little “hole” or is it nice and bright and appear to have a full view through the binoculars. This is to do with the size of the exit pupil or the rear objective. On some brands the rear lens is very small so even though the front objective is 50mm you just feel like you are not seeing the full picture. Whereas a pair with a larger exit pupil allows you see the full field of view that the 50mm provides. This affects eye strain have helps provide relief when looking through the binoculars for long periods.

You will often hear me talking about Pentax equipment and yes I am partial to them but they are one of the brands that does provide about the best balance between features and price while still providing that important eye relief.

If you liked this article and are looking for a new pair of binoculars you can support this site by clicking on the links provided below to Amazon. (we make a small affiliate commission of these links and help us to pay for the hosting on this site)