Difference Between Luminosity and Brightness

From the very beginning of human civilization, the concept of light and brightness has always been a fascinating concept for humans. In today’s world, it is almost impossible to live a normal day for any human being without having access to the concept of brightness and light.

However, there are multiple concepts emerging from this very one, and it is important to deal with some of the most crucial ones in order to develop a better understanding. Luminosity and brightness are two of such concepts. 

Luminosity vs Brightness 

The main difference between Luminosity and Brightness is that the former denotes the total amount of light that is being emitted from a particular source of light, but on the other hand, the latter denotes the exact amount of light that has been received or is being received by a particular source. Apart from this difference, these two terms differ in terms of their chemical and physical qualities as well. 

Luminosity vs Brightness

Luminosity is basically a term that represents the total amount of light radiated or emitted through a particular source of light in a given time, and usually, it is measured by simple light measuring units such as watts and joules.

A very standard parameter to measure the luminosity of any object happens to be the luminosity of the sun, as the sun happens to be the biggest source of light in the whole universe. 

But on the other hand, the term brightness denotes the total amount of light that is received through a particular source of light. It might seem like a difficult concept to conceptualize and interpret, but in reality, it is a simple one and is applied throughout our day-to-day activities.

It can also be said that the term represents the total amount of light that shines through an object. 

Comparison Table Between Luminosity and Brightness 

Parameters of Comparison Luminosity  Brightness 
Meaning  The term represents the total amount of light that emits or goes away from a particular source. The term represents the total amount of light that is received from a particular source.  
Denotes  Light emitted Light received 
Represented by Watt  Watt per unit 
Depends on Only dependent on the radiated waves. Dependent on both radiated and reflected waves. 
Affected by This factor is independent of other factors This factor is affected by certain other factors like the distance tec. 

What is Luminosity? 

The term luminosity simply shows the total amount of light that is radiated or emitted through a particular source in a particular unit of time, but in most cases, it is measured in the unit of Watt.

It can also be said that this term is a quantifiable term used to measure the amount of light that radiates from a particular medium.  

It is a very crucial term in certain fields such as astrology and photography, as many concepts are based upon the very foundation of this term.

Apart from being expressed in watt, it is sometimes expressed in another unit called candela per square. However, one very distinctive quality of this particular term is that it happens to be independent of other factors and works in its own sphere. 

Factors such as time and distance have an almost negligible effect on this particular concept, and therefore it happens to be very much free in its own way. A very interesting fact attached to luminosity is that when it comes to measuring the luminosity of stars, a very different unit is used that is usually known as solar luminosity.  

What is Brightness? 

Brightness happens to be a term that is used in our day-to-day life, but sometimes it plays a very crucial role insert in professional areas such as the area of astronomy photography and optical light.

The term, in its simplest meaning, represents the total amount of light visible to the eyes of a person.  

In other words, it can be explained as a term that denotes the total amount of light that is received in a particular object or source of light and eventually is showcased in an open environment.

This concept is slightly based upon certain other factors and can be easily affected by factors like distance and time; therefore, a very sensitive approach is needed to measure and conceptualize the whole foundation of brightness. 

It is usually expressed in the unit of Watt per unit, and two major types of waves are set to contribute to forming the total quantum of brightness that is radiated and reflected waves. In its grammatical form, the term brightness is the direct opposite of the term dullness and showcases the presence of light and visibility in some areas. 

Main Differences Between Luminosity and Brightness 

  1. Luminosity is a term showing how much light emits from something, while on the other hand, Brightness shows how much light is received. 
  2. Luminosity is basically shown in candela per square meter, while on the other hand, Brightness is shown in lumens. 
  3. Luminosity is expressed in watt while, on the other hand, Brightness is expressed in watt per unit. 
  4. Luminosity showcases emittance, while on the other hand, Brightness showcases receiving. 
  5. Luminosity is an independent factor, while on the other hand, Brightness is dependent upon factors like distance, etc.  
Difference Between Luminosity and Brightness


The concept of light is a very interesting one as it allows living beings to see the world through a completely different perspective, and this concept becomes even more relevant when something has to be done during the dark, and no source of natural light is present.

However, as simple as it seems, there are many sub-concepts available under this particular concept, and they are also very important from the point of not just knowledge but the point of use as well.

Luminosity and brightness are two such concepts that are very interconnected but still are different from one another and do too much confusion, sometimes becomes difficult to differentiate between these two. Therefore, a detailed discussion and distinction are important to do.

We marked between these two terms for a better understanding. 


  1. https://www.osapublishing.org/abstract.cfm?uri=josa-62-1-111 
  2. https://www.osapublishing.org/abstract.cfm?uri=josa-53-3-375  
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