Full Size Vs. Low Light Binoculars | Optics Trade Debates

By Maruša Justinek Sep 9, 2021

Hello and welcome to another Optics Trade debate. Today, we are going to be discussing the differences between full-size and low-light binoculars. These two terms are quite common in the world of sports optics. We at Optics Trade also categorize our binoculars, on our website, with these two terms. As they can get confusing, we decided to film this debate and help our customers differentiate between the two.

Let us begin with the differences in magnification. With low-light binoculars, the magnification is usually 7x or 8x. With full-size binoculars, the magnification can be 7x, 8x, 8.5x, 10x, 12x, 15x, and even 20x – there is a wide range of possibilities.

Interested in full sized 42 mm binoculars?

With full-size binoculars, there is a lens diameter of 40 mm—45 mm. With low-light binoculars, this is more complex. There is a combination of 7x magnification and a 50 mm objective lens and a combination of 8x magnification and a 56 mm objective lens. These two are the most common configurations. There is also 8×54 (Zeiss Victory HD) and some rare configurations such as 9×63.

What about the prism systems? With low-light binoculars, there are usually Abbe-Koenig (roof prisms) or Porro prisms, which are known to have the highest light transmission rate. When talking about full-size binoculars, they usually sport roof prisms of the Schmidt-Pechan type.

Moving on to the focusing system: with roof prism binoculars, we almost exclusively have the central focusing system – a central focusing knob. However, on the 8×56, it depends. There can be either a central focusing system or an individual focusing on each eye (Delta Optical Extreme 7×50). With low-light binoculars, individual focusing is extremely popular.

What about the exit pupil? The exit pupil is smaller on full-size binoculars. It is calculated by dividing the lens diameter by the magnification. On 8×42 binoculars, there is an exit pupil of 5.25 mm, and on 10×42 binoculars, there is an exit pupil of 4.2 mm. In comparison to low-light binoculars, the latter has a bigger objective lens and a smaller magnification, which means that the exit pupil is somewhere around 7 mm – which is ideal for low-light use, as the eye can only dilate to a maximum of 7 mm.

Simply by looking at them, it is obvious that low-light binoculars are bigger and heavier than full-size ones, which are much easier to store in a backpack. As for the price difference, when talking about binoculars from the same series, full-size binoculars are usually around 20 %–40% cheaper than low-light binoculars.

There is also a wider range of products when it comes to full-size binoculars than low-light ones (they are popular, but not every manufacturer makes them). As for the fields of use, low-light binoculars can be used, as the name suggests, low-light use, like hunting in the dusk. Full-size binoculars are for all other types of observations, such as birdwatching, observing wildlife, hunting, etc. These are great for beginners, as well as experienced users.