Phot
A unit of illumination equal to 1 lumen per square centimeter. Abbreviation: ph [Dictionary.com].
From Greek phos, genus photos - light (f, ph), obsolete unit. illumination equal to the illumination of a surface with an area of 1 cm2 with a luminous flux of radiation incident on it equal to 1 lumen. 1 ph=104 lux.
A phot (ph) is a photometric unit of illuminance or luminous flux through an area. It is not an SI unit but rather is associated with the older centimeter–gram–second system of units. André Blondel coined the name in 1921 [Moon, p.355].
A unit of the loudness of sound that measures the intensity of a sound relative to a reference tone of defined intensity and frequency. The reference tone usually has a frequency of 1 kilohertz and a root-mean-square sound pressure of 2 × 10-S pascal. The observer listens with both ears to the reference tone and the sound to be measured alternately. The reference tone is then increased until the observer judges it to be of equal intensity to the sound to be measured. If the intensity of the reference tone has been increased by n *decibels to achieve this, the sound being measured is said to have an intensity of n phons. The decibel and phot scales are not identical as the phon scale is subjective and relies on the ear's sensitivity to detect intensity changes with frequency [Law, Rennie, p.430].
Phot. Dictionary.com. Retrieved from: https://www.dictionary.com/browse/phot
Moon, P. (1942). "System of photometer concepts", in the Journal of the Optical Society of America, volume 32, number 6.
Law, J., Rennie, R. (2015). Oxford Dictionary Of Physics 7th ed. Oxford: University Press.