Defining the Optical Triangle of a Binocular
To get an idea on how optical design works, visualize a triangle with magnification at the top, field of view in the lower left corner and eye relief in the lower right corner. If you increase or decrease one of the points of the triangle it affects the other two points. For example, when you increase magnification, you have a narrower field of view and shorter eye relief. That being said, if you are looking for a super wide field of view, the lower the magnification the better.
Now we can’t leave out eye relief, another important factor, especially since more than 50% of people wear glasses. In the case of eye relief, the higher the magnification, the shorter the eye relief. Take into account that every optic is designed differently and specifications can vary from one manufacturer to another. There are also situations where the rules of the optics triangle are stretched, but only to a very small extent. In some cases the difference between the 8x and 10x in a given model may not be that significant. This is where you need to really study the specifications to determine the best option for you.
The thing to be cautious about when it comes to the optical triangle is there is such a thing as too much. Let’s say you find a binocular with an incredibly wide field of view, much greater than comparable products. Take a close look at the other specifications because chances are, that design is sacrificing one of the other key features. I have seen binos with a monstrous FOV, but the eye relief was so short that I practically had to press the eyecups into my eye sockets just to be able to see through it. In that case, the uncomfortable position of the binocular due to the short eye relief would not allow me to use the bino for any period of time, so the wide FOV was a moot point.
To sum it up, finding the right balance is the key when choosing a binocular that you can use in a variety of conditions for extensive periods of time. And that’s where TRACT shines. We purposely created our optical designs to give you that perfect balance of features and specifications to meet your needs.