Night-vision device in the context of "Available light"

Night vision is the ability to see in low-light conditions, either naturally with scotopic vision or through a night-vision device. Night vision requires both sufficient spectral range and sufficient intensity range. Humans have poor night vision compared to many animals such as cats, dogs, foxes and rabbits, in part because the human eye lacks a tapetum lucidum, tissue behind the retina that reflects light back through the retina thus increasing the light available to the photoreceptors.

Ghost hunting is the process of investigating locations that are purportedly haunted by ghosts. The practice has been heavily criticized for its dismissal of the scientific method. No scientific study has confirmed the existence of ghosts. Ghost hunting is considered a pseudoscience by the vast majority of educators, academics, science writers and skeptics. Science historian Brian Regal described ghost hunting as "an unorganized exercise in futility".

Typically, a ghost-hunting team will attempt to collect "evidence" supporting the existence of paranormal activity. Ghost hunters also refer to themselves as paranormal investigators. Ghost hunters use a variety of electronic devices, including EMF meters, digital thermometers, both handheld and static digital video cameras, including thermographic and night vision cameras, night vision goggles, and digital audio recorders. Other more traditional techniques are also used, such as conducting interviews and researching the history of allegedly haunted sites. Dowsing and Ouija boards are other traditional techniques.

A SWAT (Special Weapons and Tactics) team is a generic term for a police tactical unit within the United States, though the term has also been used by other nations.

SWAT units are generally trained, equipped, and deployed to resolve "high-risk situations", often those regular police units are not trained or equipped to handle, such as shootouts, standoffs, raids, hostage-takings, and terrorism. SWAT units are equipped with specialized weapons and equipment not normally issued to regular police units, such as automatic firearms, high-caliber sniper rifles, stun grenades, body armor, ballistic shields, night-vision devices, and armored vehicles, among others. SWAT units are often trained in special tactics such as close-quarters combat, door breaching, crisis negotiation, and de-escalation.

A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochromatic light refers to electromagnetic radiation that contains a narrow band of wavelengths, which is a distinct concept.

An image intensifier or image intensifier tube is a vacuum tube device for increasing the intensity of available light in an optical system to allow use under low-light conditions, such as at night, to facilitate visual imaging of low-light processes, such as fluorescence of materials in X-rays or gamma rays (X-ray image intensifier), or for conversion of non-visible light sources, such as near-infrared or short wave infrared to visible. They operate by converting photons of light into electrons, amplifying the electrons (usually with a microchannel plate), and then converting the amplified electrons back into photons for viewing. They are used in devices such as night-vision goggles.

Eyewear is a term used to refer to all devices worn over both of a person's eyes, or occasionally a single eye (therefore known as a monocle), for one or more of a variety of purposes. Though historically used for vision improvement and correction, eyewear has also evolved into eye protection, for fashion and aesthetic purposes, and starting in the late 20th century, computers and virtual reality.

The primary intention of wearing eyewear can vary based on the need or desire of the wearer. Eyewear comes in different forms, such as glasses, contact lenses, sunglasses and many more. Eyewear (such as glasses and contact lenses) helps most people see clearer or read. Eyewear also can be used for protection, such as sunglasses which protect wearers from the Sun's ultraviolet rays which are damaging to the eyes when unprotected, eyepatches to protect injured eyes from further damage, or goggles which protect the wearer's eyes from debris, water and other chemicals. Variants of eyewear can conversely inhibit or disable vision for its bearers, such as blindfolds and view-limiting device for humans, blinkers for horses, or blinders for birds, especially poultry. Eyewear also exists for other specialized or niche purposes, such as active shutter 3D systems and anaglyph 3D glasses for stereoscopy, and night-vision goggles for low-light environments.

A combat helmet, also called a ballistic helmet, battle helmet, or helmet system (for some modular accessory-centric designs) is a type of helmet designed to serve as a piece of body armor intended to protect the wearer's head during combat.

Helmets designed for warfare are among the earliest types of headgear to be developed and worn by humans, with examples found in several societies worldwide, the earliest of which date as far back as the Bronze Age. Most early combat helmets were designed to protect against close-range strikes, thrown objects, and low-velocity projectiles. By the Middle Ages, helmets that protected the entire head were common elements of plate armor sets. The development of firearms, cannons, and explosive weaponry rendered armor intended to protect against enemy attack largely obsolete, but lightweight helmets remained for identification and basic protection purposes into the late 19th and early 20th centuries, when developments in modern warfare saw a renaissance of combat helmets designed to protect against shrapnel, debris, and some small-caliber firearm munitions. Since the late 20th and early 21st centuries, helmets have evolved to protect against explosion shock waves and provide a mounting point for devices and accessories such as night-vision goggles and communications equipment.

A laser sight is a device attached or integral to a firearm to aid target acquisition. Unlike optical and iron sights where the user looks through the device to aim at the target, laser sights project a beam onto the target, providing a visual reference point.

Although lasers in the visible part of the spectrum are most common, invisible infrared (IR) lasers may be used in conjunction with a night vision device. As they are offset from the barrel, laser sights need to be zeroed in, much like a conventional sight, so that the beam intercepts the point of impact at a chosen distance. Devices may include one or both types of laser, with some models also incorporating a rangefinder, flashlight, or IR illuminator. Laser sights may be attached to the existing sighting mechanism, the trigger guard, via a rail system, or can be integrated into replacement components such as the guide rod or grip plates. Some variants are also incorporated into other attachments such as foregrips.