What is the Kelvin color temperature scale, and how do you use it in Blender and Unreal Engine?
In today’s tutorial, we will discuss the Kelvin color temperature scale and how we can use it to create environments with more realistic lighting scenarios.
Understanding what makes a light source feel warm or cold
Every light source out there, whether artificial or natural, has a ‘color temperature’ that defines the characteristics of that light source.
Imagine you are looking outside from your window and you don’t know what the temperature is. You say, ‘Hmm, it looks warm outside.’ Then you go outside and realize it’s actually a little bit cold!
Here’s another example: You see a building from a distance, and you can observe the lighting setup inside through its glass windows. You check the light setup and say, ‘Hmm, it feels cozy in there.’ This illustrates what I mean by ‘characteristics of the sources.’
The Kelvin color temperature scale is a scale that we created for quick access to these values, which we use in our lighting setups:
What do these numbers represent?
- Daylight (From 5000 to 6000 K, and anything in between)
- Bright White (4000K)
- Warm White (From 2700 to 3000 K, and anything in between)
- Daylight Colors: These colors are commonly used in warehouses, manufacturing facilities, and industrial areas due to their vibrant and alert characteristics. However, it’s important to note that colors within this spectrum tend to flatten red tones (In other words the light has a tendency to make red colors appear less vivid or intense) while enhancing blues.
- Bright White Colors: Bright white lighting is prevalent in retail spaces, offices, and showrooms, creating a neutral atmosphere that naturally enhances all colors.
- Warm White: This type of lighting is popular in homes, restaurants, and hospitality settings for its warm and inviting ambiance. Warm white lighting adds a yellow tint while enhancing reds and oranges.
One reason why overcast sky HDRIs (typically ranging from 6500K to 7500K, compared to direct sunlight at 5000K to 6000K) are favored in realistic renders and game footage is their ability to provide soft, diffused lighting with minimal shadows. Overcast conditions result in more uniform and evenly distributed light, contrasting with the harsh shadows and highlights created by direct sunlight. The softness of overcast lighting helps illuminate scenes more evenly, reducing the contrast between light and dark areas. These gradual transitions between light and shadow contribute to a natural and believable rendering of textures and materials.
Additionally, overcast HDRIs create a natural color balance in the environment. The absence of direct sunlight eliminates strong color casts from the sun, resulting in more neutral tones. Strong, directional light sources can significantly alter the colors of both the environment and its assets. In renders, one can immediately notice unrealistic reflections and glare effects caused by direct sunlight. Overcast HDRI setups effectively reduce specular highlights and reflections, which can be challenging to manage in outdoor scenes with direct sunlight.
Lastly, the soft, ambient lighting of overcast conditions contributes to the perception of distance and scale, enhancing the environment’s immersive and realistic feel. This quality is particularly valuable in creating believable outdoor scenes that simulate natural lighting conditions.
How to Use Kelvin Color Temperature Scale Values in Blender?
In Blender, Kelvin scale values can be utilized using a shader node called ‘Blackbody’. This node is exclusively available in the ‘Cycles Render Engine’.
To access it, select your light source, open the ‘Shader Editor’ window, and enable the ‘Use Nodes’ option located at the top of the editor.
Press ‘Shift + A’ to bring up the ‘Add’ menu, then search for the ‘Blackbody’ node. You can now adjust the temperature of your light using this node setup:
In Unreal Engine, it’s even easier to use this scale. Select your light source in the scene, and under the ‘Details’ panel, you’ll find an option to activate or deactivate the use of the Kelvin Temperature Scale:
And that’s it!
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