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Colour filters are usually made from glass to which various inorganic or organic compounds have been added. These compounds absorb some wavelengths of light while transmitting others. The compounds can also be added to plastic (often polycarbonate or acrylic) to produce gel filters, which are lighter and cheaper than glass-based filters.

Alternately, reflective filters can be made by coating a glass substrate with an optical coatingAn optical coating is a thin layer of material placed on an optical component such as a lens or mirror which alters the way in which the optic reflects and transmits light. One type of optical coating is an antireflection coating which reduces unwanted re. These filters reflect the unwanted portion of the light and transmit the remainder. Reflective filters are particularly suited for high-precision scientific work, since their exact filter band can be selected by precise control of the coating. They are however, usually much more expensive and delicate than absorption filters. Coating-based filters are often referred to as dichroicIn optics, the term dichroic has two related but distinct meanings. A dichroic material is one which either causes light to be split up into distinct beams of different wavelengths ( colours), or one in which light rays having different polarizations are, and can be used in devices such as a dichroic prismA dichroic prism is a prism that splits light into two beams of differing wavelength ( colour). They are usually constructed of one or more glass prisms with dichroic optical coatings that selectively reflect or transmit light depending on the light's wav to separate a beam of light into different coloured components.

MonochromaticSomething which is monochromatic has a single color. In physics, the word is used more specifically to refer to a electromagnetic radiation of a single wavelength. For an image the term monochrome is essentially black-and-white, but the term may be prefer filters only allow a narrow range of wavelengths (i.e a single colour) to pass.

Infrared (IR) or heat-absorbing filters are designed to block mid-infraredInfrared IR radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. The name means "below red" (from the Latin infra "below"), red being the color of visible light of longest wavelength. wavelengths but pass visible light. They are often used in devices with bright incandescent light bulbThe incandescent light bulb uses a glowing wire filament heated to white-hot by electrical resistance, to generate light (a process known as thermal radiation). The bulb is the glass enclosure which keeps the filament in a vacuum or low- pressure noble gas (such as slidecarousel slide projector, the most common form of projector A slide projector is an opto-mechanical device to view photographic slides. It has four main elements: a fan-cooled electric light bulb or other light source, a reflector and "condensing" lens to and overhead projectors) to prevent unwanted heating. There are also near-infrared filters which are used in solid state video cameras to compensate for the high sensitivity of many camera sensors to near-infrared light.

Ultraviolet (UV) filters block ultraviolet radiation, but let visible light through. Because photographic film and digital sensors are sensitive to ultraviolet (which is abundant in skylight) but the human eye is not, such light would, if not filtered out, make photographs look different from the scene that the photographer saw. This causes images of distant mountains to appear hazy. By attaching a filter to remove ultraviolet, photographers can produce pictures that more closely resemble the scene.

Neutral density (ND) filters have a constant attenuation across the range of visible wavelengths, and are used to reduce the intensity of light by reflecting or absorbing a portion of it. They are specified by the optical density (OD) of the filter, which the negative of the common logarithm of the transmission coefficient. They are useful for making photographic exposures longer. A practical example is making a waterfall look blurry when it's in bright light. ND filters can be reflective (in which case they look like partially-reflective mirrors) or absorbative (appearing grey or black).

Another kind of optical filter is a polarization filter, which blocks or transmits light according to its polarization. They are often made of materials such as Polaroid and are used for sunglasses and photography. Reflections, especially from water and wet road surfaces, are partially polarized, and polarized sunglasses will block some of this reflected light, allowing an angler to better view below the surface of the water and better vision for a driver. Polarized filters are also used to view certain types of stereograms, so that each eye will see a distinct image from a single source. Light from a clear blue sky is also polarized, and adjustable filters are used in colour photography to darken the appearance of the sky without introducing colours to other objects, and in both color and black-and-white photography to control specular reflections from objects and water.