A lightbox is a translucent surface illuminated from behind, used for situations where a shape laid upon the surface needs to be seen with high contrast.^[1]

Several varieties exist, depending on their purpose:

• Various backlit viewing devices:
  • A container with several lightbulbs and a pane of frosted glass on the top. It is used by photography professionals viewing transparent films, such as slides.^[2] This device was originally used to sort photographic plates with ease. When laid flat, it may be called a light table. Generally, a lightbox uses light similar to daylight (5,000–6,000 kelvins (K)) and has uniform light strength on the glass pane.^[3]
  • In the form of vertical panels, they can also be found mounted on the walls of hospitals and medical offices to review X-ray images (X-ray illuminator).^[4]
  • In the science field, lightboxes are often used for looking at bacterial growth and allow better visualization for PCR plates.^{[citation needed]}
  • A lighted display panel used for advertising purposes.^[5] The panel can be illuminated by fluorescent light bulbs or LED lighting strips. The efficiency of light boxes improved dramatically after the introduction of LED technology. The user inserts a graphic, which can be changed easily. Some light boxes are designed especially for outdoor purposes so they are more weatherproof.^{[citation needed]}
• An advertising format at Google Ads that allows users to click and expand an ad in order to engage with it.^[6]
• The fabric reflectors that attach to studio lighting via a connector to create soft lighting by diffusing the strobe flash are called "light boxes".^[7] They generally come in various rectangle or octagon shapes. Interior reflectors can be white, silver or gold to alter the temperature of light. Baffling inserts are also available.
• A variation of this is a box, with one open end, made of diffusing material, to allow the photographing of a sample object with no shadows. It is also called light tent or photo cube.^[8]
• A folder used on stock photography to allow a user to organize digital photos. Photos can be assigned to a viewable lightbox folder by subject, for later convenience, or used to compile unrelated photos for a specific project layout. Lightboxes also allow graphic designers to show clients options for a project in one simple uncluttered folder.^[9]
• The card-reader near the door in a hotel room, used as the main electric switch^{[citation needed]}

• Light table
• Blueprint
• Heliographic copier
• Thermal copier
• Verifax copier