Prism lighting

Special glass can move light.

It uses shapes to bend sunbeams. This moves light from bright spots to dark spots. Then, the whole room looks brighter.

People used these glass tiles a long time ago. They even used them on big ships. Some tiles were placed above doors and windows.

These tiles bend light up and deep into a room. This helps people see without using electric lights.

Today, we use new films to do this too. It is a smart way to use the sun.

Prism lighting uses special shapes to move sunlight. This helps spread light through a room.

It works through refraction. This is when light bends as it passes through a shape. It also uses total internal reflection. This is when light bounces inside a shape. These steps move light from bright spots to dim spots. This makes the whole room look brighter. It can also help people use fewer electric lights.

In the past, people used glass prism tiles. They put them above doors or windows. These are called transom lights. They bend light up and deep into a room. This is better than lighting only the floor.

Prisms were used in many places. They carried light to decks on ships. They even lit up basements under sidewalks. Some artists made beautiful designs for them. Frank Lloyd Wright made over forty designs.

Today, we use new films to move light. These films are thin and sticky. Some films use tiny prisms. Other films use small slits to reflect light. They can even replace thick blinds.

Prism lighting is a clever way to move sunlight. It helps spread light through a whole room. This method is called anidolic lighting. It works by moving light from bright spots to dim spots. The human eye does not see brightness in a straight line. If you halve the light, the room only looks slightly dimmer. Moving light to dark corners makes a space feel much brighter. This can also help people use less electric light.

This system works using two main tricks. The first is refraction, which is when light bends as it passes through a shape. The second is total internal reflection. This is when light bounces inside a shape. Many small prisms can be joined together into a sheet. This sheet is a bit like a Fresnel lens. However, it does not focus the light into a point. Instead, it just redirects the beams to new places.

People used prism lighting for a long time. It was very popular from the 1890s until the 1930s. During that time, electric lights were not yet common. When cheap electric lights became popular, prism lighting became unfashionable. Mass production of these systems ended around 1940. However, the technology is having a revival in the 2010s. We now use new materials like acrylic to make them.

There are many different kinds of prisms. Deck prisms once carried light to the upper decks of ships. On land, sidewalk lights used prisms to light up basements. Many people used prism tiles as transom lights above doors. These tiles bend light upwards to reach deep into a room. One company even sold tiles with nine different prescriptions. These prescriptions gave different angles for the light to bend. Some tiles were even used to bend light around pillars.

Today, we have very modern ways to redirect light. We can use a thin, flexible sheet called Daylight Redirecting Film. This film is a peel-and-stick type of material. Some films use tiny prisms moulded into the acrylic. Other films use small slits to reflect light upwards. These films can even replace thick, dark blinds. Some films send light to the ceiling to spread it out. Other films can send light nearly horizontally across a room.

Prism lighting is a specialized method used to improve how light is distributed within a space. It is a form of anidolic lighting, which means it focuses on redirecting light rather than just concentrating it. This technique is primarily used to manage natural daylight. By moving light from the brightest areas of a room to the dimmest areas, the entire space appears much brighter to the human eye. This happens because the human eye's response to light is non-linear. If you halve the amount of light in a room, it does not appear half as bright; it only looks slightly dimmer. Therefore, redistributing light can create a more comfortable level of illumination and reduce the need for artificial electric lights.

The mechanism behind this process relies on two optical principles: refraction and total internal reflection. Refraction occurs when light bends as it passes through a material like glass or acrylic. Total internal reflection happens when light bounces off the inside surfaces of an object. Many small prisms can be joined at their edges to create a single prism sheet. This sheet functions similarly to a linear Fresnel lens. However, while a Fresnel lens is designed to focus light into a single point, a prism sheet is used for anidolic lighting to redirect beams. This allows light to be sent to different parts of a room instead of being concentrated.

There are several distinct types of prism systems designed for different environments. Deck prisms were used on ships to carry light through upper decks to the decks below. On land, sidewalk lights used prisms to provide illumination for basements and vaults. Prism tiles were another common type, often used vertically as a transom light above windows or doors. These tiles can be built into skylights, sloped glazing, or movable canopies. They are designed to bend light upwards so it penetrates deep into a room. This prevents the light from only hitting the floor immediately next to the window.

Historically, prism lighting saw a period of great popularity from the 1890s through the 1930s. During this era, electric lighting was not yet cheap or common. As inexpensive electric lights became widespread, prism lighting became unfashionable. Mass production of these systems eventually ended around 1940. However, the technology has seen a revival in the 2010s due to the development of new materials. Modern prismatic panels are often made of acrylic, which serves as a contemporary version of the old glass tiles. These modern panels can still be mounted on adjustable canopies just like their predecessors.

The manufacturing and repair of these systems have evolved over time. Older glass elements were often cast and then cut and polished. To join individual prism tiles, makers used strips of zinc, lead, or electroglazed copper, similar to the methods used in stained glass. Because many old tiles followed standard designs, a salvage market exists for replacements. Damaged tiles can sometimes be repaired or reinforced with hidden bars. Today, many daylight redirecting films are made from acrylic. These films are thin, flexible, peel-and-stick sheets that can be applied to windows.

Modern daylight redirecting films (DRF) offer two main ways to move light. Some films are moulded with tiny prisms, acting as miniature prismatic panels. Other films use thin, near-horizontal voids or slits that reflect light hitting their top surfaces upwards. These reflection-based films are quite transparent, but they tend to send light toward the ceiling. Refraction-based films are more translucent, but they allow for finer control over the light's direction. By using different prism shapes, the film can refract light at many different angles. This allows the light to be sent nearly horizontally across a room, making the film a useful substitute for opaque blinds.

Architectural design has utilized these tools to shape how we experience buildings. Sophisticated systems were developed to send light across rooms at specific angles. One company even offered tiles with nine different prescriptions to provide different angles of refraction. Architects could use different prescriptions in one window to disperse light vertically or bend it horizontally around obstacles like pillars. Famous architects even contributed to the art of the medium; Frank Lloyd Wright created over forty different prism tile designs. Some believe that these bright, light-filled spaces helped drive the trend away from dark, subdivided Victorian interiors toward modern, open-plan designs.