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Color: Luminosity in HSL

Explore how Luminosity works within the HSL color model.


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We explored the HSL color model broadly previously -- now we will look at Luminosity, one of its three properties. So what is Luminosity? Luminosity is the value that spans from pure black (darkest) to pure white (lightest), as can be seen in Figure 1, below.

Luminosity spans from darkest to lightest
Figure 1: Luminosity spans from darkest to lightest

Now how does Luminosity influence any color? Let's take blue for example -- look at the top bar in Figure 2, below where you can see a blue shape. If we add the Luminosity bar to it, which is the same as what you saw in Figure 1, above -- we will then see the results as shown within the bottom bar in Figure 2.

Luminosity can influence colors
Figure 2: Luminosity can influence colors

Now let us see how Luminosity influences six hues of the RGB color model, as shown in Figure 3, below.

Luminosity can influence any color hue
Figure 3: Luminosity can influence any color hue

The three primary colors in the RGB model (Red, Blue, Green) as well as the three secondary colors Yellow, Cyan, Magenta) all have a Luminosity value of 128, as can be seen within the table below:

Color H S L Swatch
Red 0 255 128  
Yellow 42 255 128  
Green 85 255 128  
Cyan 127 255 128  
Blue 175 255 128  
Magenta 213 255 128  

That's not surprising -- and this makes it easy for us humans to understand that all basic colors (primary and secondary) have some common traits. You can see that 128 is the value at the center of each of the bars you see in Figure 4, below.

Pure hues are halfway through the Luminosity bars
Figure 4: Pure hues are halfway through the Luminosity bars

Let us now change the Luminosity values of all these 6 colors -- we changed the Luminosity of all 6 colors to 192 to end up with lighter variations of the same colors -- this is almost the same as mixing some white into the basic colors!

Color H S L Swatch
Red - Light 0 255 192  
Yellow - Light 42 255 192  
Green - Light 85 255 192  
Cyan - Light 127 255 192  
Blue - Light 175 255 192  
Magenta - Light 213 255 192  

Look at the same color bars again in Figure 5 below -- you can see that these values match where the Luminosity is set at 192 -- this is more towards white (the right side).

Luminosity slides towards white
Figure 5: Luminosity slides towards white

Next let us change the Luminosity value to something lower such as 64, so that we end up with darker variations of these colors -- this is akin to mixing some black into these basic colors, as can be seen in the table below.

Color H S L Swatch
Red - Dark 0 255 64  
Yellow - Dark 42 255 64  
Green - Dark 85 255 64  
Cyan - Dark 127 255 64  
Blue - Dark 175 255 64  
Magenta - Dark 213 255 64  

Look at the same color bars again in Figure 6 below -- you can see that these values match where the Luminosity is set at 64 -- this is more towards black (the left side).

Luminosity slides towards black
Figure 6: Luminosity slides towards black

Let’s take this experiment to its logical conclusion now, and change all Luminosity values to an even lower value, such as 16 – you will see that the color values we end up with are almost black, as can be seen in the table below.

Color H S L Swatch
Red - Darker 0 255 16  
Yellow - Darker 42 255 16  
Green - Darker 85 255 16  
Cyan - Darker 127 255 16  
Blue - Darker 175 255 16  
Magenta - Darker 213 255 16  

Look at the same color bars again in Figure 7 below -- you can see that these values match where the Luminosity is set at 16 -- this is almost black.

All colors are now almost black
Figure 7: All colors are now almost black

If we now change the Luminosity values to 0 (zero) for all colors, it does not matter what Hue or Saturation values they have – they will all be black! This reasoning is easy to explain using an analogy. In a very dark room, if you switch off the light you will be left with pitch darkness, and any object of any color will appear black. That’s precisely what's happening here too!

The reverse is also true. If you are blinded with too much light, everything will appear white. And that’s exactly what will happen if you change all Luminosity values to 255.

So the main takeaway from Luminosity is that you can make as many changes as you want to your Hue and Saturation values – but if your Luminosity values are not set optimally -- then all you will see is either black or white! That’s the reason we decided to explore Luminosity before Saturation and Hue, the other two properties.

See Also:

Color: HSL
Saturation
Hue

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