Spirit level in the context of Videography

A plumb bob, plumb bob level, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical direction as a reference line, or plumb-line. It is a precursor to the spirit level and used to establish a vertical datum. It is typically made of stone, wood, or lead, but can also be made of other metals. If it is used for decoration, it may be made of bone or ivory.

The instrument has been used since at least the time of ancient Egypt to ensure that constructions are "plumb", or vertical. It is also used in surveying, to establish the nadir (opposite of zenith) with respect to gravity of a point in space. It is used with a variety of instruments (including levels, theodolites, and steel tapes) to set the instrument exactly over a fixed survey marker or to transcribe positions onto the ground for placing a marker.

Fluorescein is an organic compound and dye based on the xanthene tricyclic structural motif, formally belonging to triarylmethine dyes family. It is available as a dark orange/red powder slightly soluble in water and alcohol. It is used as a fluorescent tracer in many applications.

The color of its aqueous solutions is green by reflection and orange by transmission (its spectral properties are dependent on pH of the solution), as can be noticed in bubble levels, for example, in which fluorescein is added as a colorant to the alcohol filling the tube in order to increase the visibility of the air bubble contained within. More concentrated solutions of fluorescein can even appear red (because under these conditions nearly all incident emission is re-absorbed by the solution).

A water level (Greek: Aλφαδολάστιχο or (υδροστάθμη) [Alfadolasticho]) is a siphon utilizing two or more parts of the liquid water surface to establish a local horizontal line or plane of reference. It is used to determine the apparent inclination of an object or surface and for matching water level elevations at locations that are too far apart for a spirit level to span.

The simplest water level is a section of clear tubing, partially filled with water. Water is easily procured for use, and easily discarded after use. The ends are held vertical, and the rest of the tubing lies on the ground or floor. The water level at each end of the tube will be at the same elevation, whether the two ends are adjacent or far apart, so a line between them will be horizontal at its midpoint and a shed base, building foundation or similar structure laid out using several such lines will be "horizontal" within building tolerances on any scale over which use of a water level is practicable. Water levels have been used for many years. The water level is lower-tech than the laser level, but it can be more accurate over long distances, and works without a sightline, such as around corners. To avoid error, all of the water should be at the same temperature. Other sources of error include difficulty reading due to meniscus.

Lāhainā Noon, also known as a zero shadow day, is a semi-annual tropical solar phenomenon when the Sun culminates at the zenith at solar noon, passing directly overhead. As a result, the sun's rays will fall exactly vertical relative to an object on the ground and cast no observable shadow. When this occurs at a given location, the location is Earth's subsolar point. A zero shadow day occurs twice a year for locations in the tropics (between the Tropic of Cancer at approximate latitude 23.4° N and the Tropic of Capricorn at approximately 23.4° S) when the Sun's declination becomes equal to the latitude of the location, so that the date varies by location. The term "Lāhainā Noon" was initiated by the Bishop Museum in Hawaii.