What is a Blue Flashlight Lens Used for?

Last Updated on May, 2024

Night vision, seeing the dark, is why you need a flashlight. With flashlights coming in a range of colors, what is explicitly the blue flashlight used for?

Each COLOR flashlight serves a particular purpose. While some are better for HUNTING, others help improve your night vision. 

So what exactly is blue light used for?

Quick Summary

Blue flashlights are used for hunting, forensic science, fishing, detecting leaks in equipment, seeing through fog, and map reading.

Blue light is used to detect blood, other bodily fluids, chemicals, and oil.

Blue light has a variety of applications, from hunting and fishing to forensic science and industry use.

What is the Purpose of Blue Light?

Blue Flashlight

Blue light doesn’t provide the same level of clarity as green light or an improvement in night vision as red light. The primary use of blue light is to detect chemicals, oils, blood, and other bodily liquids that the naked human eye cannot detect. 

There are various uses of blue light; however, the use in FORENSIC science is something you may have heard about. Blue light is often used in crime scenes to detect trails of blood or other bodily fluid. 

Various colors of light have varying features and uses. Blue light, in particular, has six main uses.

What is a Blue Flashlight Used For? – 6 Uses of Blue Flashlight Lenses

Blue flashlight lenses can be purchased separately; otherwise, blue flashlights are also available in the market: blue flashlight lenses work to transform natural light into blue light.

Here are six KEY uses of a blue flashlight lens (emits blue light.)

1. Hunting

Civilians often use blue light in hunting. This is because blue light has the capability to trace and detect trails of blood and other bodily fluids. 

Hunters use blue light to track wounded prey. After the prey has been shot and wounded, the blue lights come in handy when searching for the HUNTED prey.

You would be able to detect and trace blood stains amidst the forest foliage. 

It is also put to use by bow hunters who can trace used arrows (that contain blood) and find them using a blue light.

Since a good quality arrow can set you back $100, using blue light to find used arrows can be very useful.

a human using blue flashlight in forest

With blue lights being commercially available (blue flashlights), hunters often include them in their hunting arsenal to find wounded prey.

Here’s a list of the best flashlights that will help you when hunting.

2. Forensic Science

Blue light is most famously used in Forensic Science. If you’ve watched a crime show on Netflix, you may have already seen depictions of how blue light is used in Forensic Science. 

Blue light has the ability to detect blood and other bodily fluids. This makes it a handy tool in crime scene investigation.

Blue light can even detect and trace chemicals and oil, all of which are put to good use in Forensic Science. 

In combination with luminol, blue light is used to make invisible stains appear glowing and visible.

a human using a blue flashlight for Forensic Science

These blue lights have helped many forensic bodies both investigate and solve crimes. Though blue light isn’t the only color of light used in forensic science, blue light has a practical application in this field.

3. Fishing

Fish scales and body oils glow in the presence of blue light. This is why blue light is also used in fishing to detect fish.

***Unlike with hunting, the blue light is NOT used to detect blood, but detect the whole fish (it works like a radar.) 

Fishermen use a variety of colors of fishing light (green, white, etc.) Blue light, in particular, is used to detect fish in water. The blue light works to lure in fish that dwell in saltwater.

This, however, does not work with freshwater fish. 

That being the case, blue light is still used to detect fish, even in freshwater. 

blue flashlight working near the water

Fishermen have used blue light flashlights to find fish for a long time. It is one of the more reliable techniques in fishing, intended to find and catch fish in dark waters. 

4. Find Leaks in Equipment

Industrially, blue light is used to detect chemical and oil leaks in equipment.

Though you may not have thought of pointing a blue flashlight in your garage to find an oil leak in your car, you CAN!

Often, oil and chemical leaks are easily fixable if spotted early. This is why blue light (blue light flashlights) are so useful.

They can help in the detection of early leaks, which can help industries save a lot of money (fixing a small leak is more manageable.)

Industry professionals often rely on blue light to detect even the TINIEST drop of oil from a leak somewhere. Even if the leak is a faint one, a blue light will work to detect it. 

a human using blue flashlight for Find Leaks in Equipment

For instance, farmers use blue flashlights to detect hydraulic leaks in farm equipment. You, too, can use a blue flashlight to check any equipment (including vehicles) for oil and chemical leaks. 

5. Fog

Blue light cuts through fog incredibly well. In comparison to a regular flashlight, a blue flashlight lens will work to penetrate fog, improving visibility.

This can be very useful for people living in foggy conditions.

Though other colors of light (such as white light) can too penetrate fog, blue light is the ONLY option when dealing with DENSE fog. 

Riding anything in the fog can be dangerous. Using a blue light will make it MUCH easier for you to see through the fog, making this a very practical use of blue light flashlight lens.

a human using blue flashlight in Fog

Hence, if you find yourself in foggy conditions, remember that a blue flashlight lens could really come in handy when dealing with fog.

6. Map Reading

Unlike flashlights of other colors, blue light does not wash out red lines. The red lines are a vital part of a map, which are NEEDED to understand and read a map properly.

This is why pilots and sea captains use blue light to read maps at night. 

In comparison to natural or white light, blue light can make it easier to study a map at night. 

This can be very useful when hiking or camping or whenever studying a map becomes necessary.

Hence, if you wander at night with a map (hiking), keep a blue flashlight, which will likely prevent you from getting lost. 

a human using blue flashlight for Map Reading

Benefits of Blue Light Flashlight Lenses

Considering the various uses of blue light compared to other lights, blue flashlights have various benefits.

For instance, it can help you find an oil leak in your car. It can also help you cut through the fog or even read a map at night. Considering the various practical uses of blue light, it can be handy to own a blue flashlight or a blue flashlight lens for your regular flashlight.

Blue light performs specific functions in comparison to the regular light of a flashlight. Coupled with their particular use in forensic science, the wide variety of applications of blue light provides the main benefit of opting to use a blue light flashlight lens. 

Why Use a Blue Filter on a Flashlight?

Blue Flashlight

This answer rests on why you need blue light (the uses of blue light.) Blue light isn’t the only spectrum of light and has specific purposes. Apart from the list of uses, we discussed in this article, having a blue flashlight doesn’t really provide for anything more. 

Sure, you can use a blue flashlight as you would a regular flashlight; however, a blue light will become more useful in finding a leak, when hunting or when reading a map at night. 

Hence, a blue filter for your flashlight can be very useful depending on where you intend to use blue light. 


Blue light has many specific uses making them useful for various purposes. Whether hunting or seeing through fog, blue flashlight lenses can come in handy based on purpose. 

Though industry professionals in forensics use them, they can easily come in handy when checking for an oil leak in your car. 

Blue light has both industry and commercial use; however, it is not the only color of light of flashlights. Here, have a read of this article on Multi-Color Flashlights


Yes, blue flashlight lenses are good for fog, as blue light is the most effective color for cutting through dense fog.

Yes, blue flashlight can be used in hunting as it is an effective tool for detecting traces of blood and other bodily fluids, helping hunters to track down and locate wounded prey.

Yes, blue light is good for map reading as it allows users to see red lines on maps and enables them to study a map at night effectively.

Yes, blue light can be used to detect oil and chemical leaks industrially, as well as on farm equipment and vehicles.

Yes, blue light is used in fishing, specifically in saltwater fishing, to identify the position and abundance of fish in the water. It does this by illuminating fish scales and body oils, making them visible in dark waters.

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Dillon Morrison
I have been involved in the flashlight community since 2007. My brother has a flashlight shop from where I have tested and reviewed more than 600+ different types of flashlights. You can find more about me here.

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