How To Choose Binoculars For Low Light Conditions (Best UK Guide)
There are many activities that require binoculars when the light is fading, or during early morning, predawn light. Many naturists, hunters, wildlife watchers or even sailors needing to navigate into safe harbours, will all need the extra vision provided by binoculars especially before dawn or as dusk approaches. That’s where low light condition binoculars come in.
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What’s The Difference Between Low Light And Night Vision Binoculars?
There are both similarities and distinct differences between low light condition binoculars and night vision binoculars. Let’s start with explaining these differences before we look at what to look for in low light binoculars.
What Are Night Vision Binoculars?
Night vision binoculars make use of the technology used in low light binoculars but also employ more advanced technology too. Night vision binoculars use amplifiers to electronically magnify any ambient light as well as flooding the area with infrared light that can be picked up by binoculars optics. Some night vision binoculars also employ thermal imaging scanners to hone in on heat signatures.
Night vision binoculars can operate in absolute darkness, but are far more expensive and contain more intricate and complicated internal equipment. They are also heavier due to the batteries stored onboard that power the equipment.
What Are Low Light Binoculars?
Low light binoculars look very much like regular binoculars, but also make use of lenses and mirrors to make the most of any available light. They don’t use any power source, relying solely on natural light but enhanced by their internal components. Low light binoculars work best where there is some natural light, either the emerging daybreak or a full moon.
Low light binoculars rely on their objective lens to gather light, all binoculars use the objective lens to increase the field of view and to allow light to enter, but it’s far more important in low light conditions.
The objective lens is the one that’s furthest from your eye, closest to the object you are viewing. The size of the objective lens dictates how much light can enter the binoculars, which in turn, illuminates the image you can see through the binoculars. Large objective lenses are responsible for gathering light and providing a wider field of view.
For low light binoculars, the larger the objective lens diameter, the more light the binoculars can gather. We recommend a minimum of 50 millimeters diameter objective lens for low light binoculars.
Field Of View (FoV)
The field of view is the width of the image you can see through the lens of the binoculars from left to right while looking straight ahead. A wide field of view allows you to see more through the binocular lens. With the field of view there is a direct relationship between large objective lens, low magnification and a wide field of view.
Most low light binoculars will have relatively low magnification values. It sounds counter productive but if the magnification is too large, you will see less. Anything above 10x magnification will be blurry due to the natural shakiness we all have when holding any object out in front of us for long periods of time. That natural shake will be magnified by the amount of magnification of the lens.
The magnification and objective lens diameter are usually displayed together and look something like 10×50. That means a magnification of 10x with an objective lens diameter of 50mm.
The exit pupil is the diameter of the light that emits from the binoculars onto our pupils. At night the human pupils when at rest measure about 7mm. So any low light binoculars with a 7mm or greater exit pupil will allow enough light for us to see the image through the lens.
To calculate the exit pupil, divide the objective lens diameter by the magnification – 7×50 has an exit pupil of 7.14 – 50÷7=7.14 So low magnification and high objective lens diameter equals large exit pupil.
Better Light Transmission
The rate of light transmission is vitally important in low light binoculars because in low light conditions, as much light as possible needs to reach the eye.There are a few requisites to improve light transmission they include;
- Top Quality Glass
The best quality glass for binocular prisms is BAK-4 glass which has less imperfections.
- High Quality Lens Coatings
Fully multi-coated lenses will improve brightness, contrast and light transmission.
- Prism Type
Abbe Koenig prisms have far better light transmission for low light binoculars (Schmidt-Pechan are fine for daylight binoculars).
Abbe Koenig prisms are usually found in Porro prism binoculars, Schmidt-Pechan are usually found in roof prism binoculars.
Extra low dispersion glass is used in top quality optics to provide sharp images with no colour fringing, If ED glass is in the specs, you’re buying a quality pair of binoculars.
Waterproof And Fog Proof Binoculars
With all the good intentions in the world, you and your binoculars will get wet at some point. We live on a planet that consists of 71% water, and in a country where the main difference between Summer and Winter is the temperature of the rain. It makes sense to invest in waterproof binoculars.
There is a coding system set up by the industry that determines how waterproof items are. It can make confusing reading, so suffice it to say that any binoculars with an IPX code of 6 or above will be waterproofed enough for general usage.
Fog proof binoculars have all of the air purged from them and replaced with either nitrogen or argon. As these gasses contain no moisture, they cannot react with fluctuating temperatures to cause fogging of the lenses. As the gas is sealed inside the lens tubes, no dust or microbial detritus can enter, keeping your binoculars free from mould spores etc.
Frequently Asked Questions
The best size binoculars for low light conditions are low magnification, high objective lens diameter binoculars, something like 7×50 or 7×56. These have a large exit pupil which means the image you see will be brighter.
The best magnification for binoculars for tracking wildlife is between 7x to 10x. Anything above 10x will magnify our natural shake so much that the image will appear blurred.