<p>is there a way to output the power in watts from an R, G and B value? I know there are many formulae to get perceived brightness but is there one to get an objective amount (relative or otherwise)?</p>
<p>This is for an experiment I am working on which basically requires radiance to stay constant between images but I am not sure how to calculate radiance fro an image.</p>

CC BY-SA 4.0
2023-07-04T14:30:44.063Z
Are you looking for the _actual_ output power that a specific display device will be producing, or a theoretical ideal result given the definition of the color space in use? (In the former case, there are enough non-idealities that you might need to measure the actual output to build a model.)
Kevin Reid
CC BY-SA 4.0
2023-07-04T16:26:44.613Z
@KevinReid theoretical ideal result given the definition of the color space in use
Dom DJ
CC BY-SA 4.0
2023-07-04T17:08:03.697Z
You would certainly need to do it as a relative value rather than a value in watts. If you say that a fully white image produces a power output of 100%, then you could estimate what percentage of that each image generates. I think it could only be an estimate, as different screens could output different amounts of energy to display the same colour, depending on the specific wavelengths being generated.
Timothy Maguire
<image-processing>
How can I get an Irradiance or power value from RGB?
Dom DJ
# How can I get an Irradiance or power value from RGB?

(Asked by: username_0 on 2023-07-03)

is there a way to output the power in watts from an R, G and B value? I know there are many formulae to get perceived brightness but is there one to get an objective amount (relative or otherwise)?

This is for an experiment I am working on which basically requires radiance to stay constant between images but I am not sure how to calculate radiance fro an image.

**Tags:** image-processing

> **Comments:**
> **username_1**: Are you looking for the _actual_ output power that a specific display device will be producing, or a theoretical ideal result given the definition of the color space in use? (In the former case, there are enough non-idealities that you might need to measure the actual output to build a model.)  
> **username_0**: @username_1 theoretical ideal result given the definition of the color space in use  
> **username_2**: You would certainly need to do it as a relative value rather than a value in watts. If you say that a fully white image produces a power output of 100%, then you could estimate what percentage of that each image generates. I think it could only be an estimate, as different screens could output different amounts of energy to display the same colour, depending on the specific wavelengths being generated.  

---

## 0 answers

