This yellow is brighter than this blue???

[itsmyacccountitsnowornever]

Hi, first I want to see if this post goes through but this yellow is meant to be brighter that this blue, if you change it to greyscale with the "Hue/Saturation" tool this:

Turn it to greyscale that way and we get this:

See that the blue is converted as DARKER than the yellow.

 

Does the blue look darker than the Yellow to ANYONE?

 

Also if the human eye really worked this way why would white with equal amounts of red, green and blue look white at all, shouldn't it look yellowy?

 

It's hard to see why this should be?

 

Update:  I rotated the hue on the first image and then in a separate process reduced the saturation to zero, it gave me this:

 

That looks a lot more what I would expect the first image to look like converted to greyscale than the second image shows where it has the words as just a little darker than the background.

 

It seems there is a conspiracy against most people's favorite colour, blue.

Edited January 28, 2021 by itsmyacccountitsnowornever
addition

[toe_head2001]

I won't pretend to fully understand the calculations to obtain the Intensity of RGB values, but you can read an answer provided here:

https://computergraphics.stackexchange.com/questions/5085/light-intensity-of-an-rgb-value

 

If you're not satisfied with the Intensity values returned by Paint.NET's desaturation, there are Effect plugins that provide alternatives.

For example: https://forums.getpaint.net/topic/113452-black-and-white-plugin/

[Ego Eram Reputo]

The different RGB channels contribute to the intensity by different amounts. I use this formula to calculate the intensity of a pixel:

 

(iColor.R * 0.299) + (iColor.G * 0.587) + (iColor.B * 0.114)

 

As you can see, the weighting given to blue color channel is 0.114, much less than Red (0.299) or Green (0.587).