How to get colors with the same perceived brightness?

Question

Is there a system of tools / programs / colors that allows you to get colors of the same brightness (perceived brightness)?

Let's say I select a color (determine the RGB values) and the program gives me all the colors around the color wheel with the same brightness but different hues?

I have not seen such a tool yet, all I came across is three different color brightness algorithms:

(0.2126*R) + (0.7152*G) + (0.0722*B) (0.299*R + 0.587*G + 0.114*B) sqrt( 0.241*R^2 + 0.691*G^2 + 0.068*B^2 ) 

Just to be clear, I'm talking about color brightness / perceived brightness or what you want to name - an attribute that occurs that we perceive a red tint brighter than blue, for example. (Thus, 255.0.0 has a higher brightness value than 0.0255.)

PS: Does anyone know which algorithm is used to determine the color brightness on this website: http://www.workwithcolor.com/hsl-color-picker-01.htm It looks like they have not used any of the published algorithms .

Answer 1

In the HSL color picker you are attached to, it looks like they are using the 3rd level equation given here and then making it a percentage, So the equation is:

 L = (100 * 0.5 * (max(r,g,b) + min(r,g,b))) / 255 

Edit: Actually, I just realized that they have the L value and the Lum value indicated on this color set. The above equation refers to the value of L , but I do not know how they reach the value of Lum . It does not seem to correspond to any of the standard equations.