Illuminance vs. Luminance: Know Differences!
Richa Parmar born & brought up in Navsari, a town in Gujarat picked up a degree as an Architect from The Maharaja Sayajirao University of Baroda after pursuing Diploma in Architecture Assistantship from Surat. Passionate in the field of designing & creativity, she tries to do a lot of research in her field & implements the same in her work. She has been creating excellent imaginative designs that fit in the budget & also fulfils the needs of clients. Her inclination towards nature has made her take up a lot of challenging assignments in the subject of “landscape” and also has made her initiate to write blogs. Presently she works as an Senior Manager cum Architect Blogger for “Gharpedia” portal. Her blogs keep long term impact on the readers’ mind which shows her commitment to producing excellent results by attracting traffic to her writings. Regardless of her tasks, she also briefs her team for streamlining the process more effectively within proper strategies. Looking at her softer part in life, she loves painting, reading & travelling. She is a hardcore fan of dogs and also has one at her home. You can reach her at LinkedIn, Facebook, Twitter, Instagram, Pinterest, Quora & Medium.
In the lighting world, many of the lighting terms often sound very similar but have vast different meanings which can lead you to the confusion and a misunderstanding of lighting terminology. Illuminance and luminance both the terms are the most confusing term and are more or less used incorrectly by people, sometimes even by the people in the same industry!
- Simply the illuminance determines the amount of light that covers a surface. Illuminance is invisible, generally it is light passing through space and not seen unless you look at the source (e.g. a light bulb) or a surface it reflects off or we can only see luminance.
- The illuminance or light level is the amount of light energy reaching a given point on a defined surface area, which is the luminous flux (i.e. lumens) per square meter.
- In other words, At a point on a surface, the ratio of the luminous flux incident on an infinitesimal element of the surface containing the point under consideration to the area of the element.
- (NOTE — The unit of illuminance (the measurement of illumination) is Iux which is 1 lumen per square meter.)
- Luminance is an amount of visible light that comes to the eye from surface or it can also be said as a state or quality of radiating or reflecting light.
- Luminance is often used to describe emission or reflection from flat or diffuse surfaces. The luminance indicates how much luminous power will be detected by an eye looking at the surface from a particular angle of view.
- Therefore luminance is thus an indicator of how bright the surface will appear.
- Note: Luminance = Illuminance + Reflection
- In other words, it is the quotient of the luminous intensity in the given direction of an infinitesimal element of the surface containing the point under consideration by the orthogonally projected area of the element on a plane perpendicular to the given direction. The unit is candela per square metre (cd/m2).
- Standard unit for illuminance is Lux (lx) which is lumens per square meter (lm/m2).
- Typical illuminance values/ranges for our understanding are as follows:
|1 lx||Full moon|
|10 lx||Street lighting|
|100-1’000 lx||Workspace lighting|
|10’000 lx||Surgery lighting|
|100’000 lx||Plain sunshine|
- The SI unit for luminance is candela per square metre (cd/m2).