Monoculars. Compact and handy viewing

Most folks would be familiar with binoculars. These are effectively two, small telescopes side by side that are carefully aligned together to look forward. You may have also seen optical gizmos called a monocular.

This looks like one side of a pair of binoculars and there are some advantages using them compared to the traditional binos. There's also a few downsides and we'll cover those first. 

One eye vs two eyes

What's the advantage of using binoculars vs a monocular?

Leaving aside those with impaired or no vision in one eye who are well aware of this, you might be surprised at just how much we instinctively rely on our both of our eyes for the full view of field of our vision. Our brain automatically combines information received from our left and right eyes into one view, edits out things that are in the way such as your nose and then seamless produces a big picture. (We talked about this when discussing field of view in last month's blog that you can read here.) What's more, we use both eyes for depth perception or 3D vision and the two sides of binoculars help to provide this. 

You can try two quick experiments. First of all, take a look a look around across the street or around your backyard, or somewhere similar. Now cover one eye and try the same thing. You'll be surprised at just how much of your "view" that suddenly disappears.  Now plonk a few objects on the table a metre or two in front of you. It'll be pretty obvious which ones are further away from you, even if by only a small amount. Shut one eye and you'll quickly see the differences in distance aren't so clear. 

We rely on this stereo vision produced by slight differences in what our left and right eyes see, called Stereopsis, to view the world in 3D.  Depth perception and knowing which objects are further away in the distance can still be perceived with binoculars and more so in roof prism models which have wider set lenses. 

Nikon Action 10x42 Binoculars showing the wideset lens which helps with distance, 3D vision. 

Finally, many people find using binoculars more comfortable, especially when observing for longer periods. Two hands let you balance them and you're not holding them to one side like you would with a monocular.  

What's the advantage of a monocular?

There are two main reasons. Cost and convenience. 

With a monocular, as it's essentially just one side of a more traditional pair of binoculars, you'll be buying a far more affordable optical device. The optics of both sides of binoculars not only need to held carefully in parallel, but their bodies are also more expensive to produce. Their focusing mechanism is also more complex as both barrels require the same focus movement, as well as allowing for people with slightly different left and right eye focussing which further adds to the cost. (This is called a Diopter adjustment and found on almost all binoculars.)

The convenience advantage simply arrives because a monocular of the same diameter as a pair of binoculars will be half the size or less. This makes it more compact and easier to transport. If you're ok with losing the wide field viewing that binoculars off and the lack of 3D vision isn't a problem for you, then smaller size of a monocular and lower cost might be attractive for you. 

Monocular magnification

Monoculars use the same naming conventions as binoculars and spotting scopes. The first number is the magnification followed by an "x" and then the size of the front lens in mm.

So, a "ten by forty two" written 10x42 is 10 times magnification with a 42mm diameter front lens. 

There's the same general advice around finding roughly the right magnifications and lens size for your interests and lifestyle also apply. For bird watching, an 8x42 or 10x42 would be ideal.

What are some different monoculars?

For example, this affordable  GERBER 10x42 Monocular would be about half the weight and size of comparable 10x42 binoculars. You might be better off with binoculars for some activities such as bird watching where you want as wide a field as possible to help spot our feathered friends. For distant scenery or observing slow moving objects such as boat, a monocular such as this might help, especially where portability is important. 

Stepping down to something that's truly pocket sized but with remarkable image quality, this small Leica Monovid 8x20 monocular offers great viewing of distant scenery and wildlife in a small package.

Its high quality optics make it about the smallest optical device we carry that offers bright and clear viewing that are comfortable for extended periods of time. 

It's not uncommon for some monoculars to be able to focus on objects at fairly close up. In the case of this Leica monocular, as it can focus as close as 1.8m. This opens up some possibilities for closeup nature viewing. We also have some of our Leica customers using it when visiting museums and taking to concerts.

To wrap up