How to make color black-and-white?

What is the rule of any color can be converted to black and white? This can be seen in Photoshop when set to "grayscale".
PS About the average value of thought was, but it did not.

October 3rd 19 at 01:56
2 answers
October 3rd 19 at 01:58
Solution

1) RGB -> HSB
2) reset saturation
3) convert back HSB -> RGB

October 3rd 19 at 02:00

Rasanya colors have different sensitivity people eye, respectively, to average not.

If you mean the formula, here's one option:
G = 0.21 * R + 0.71 * G + 0.07 * B

Do not understand where exactly these factors? - joanie4 commented on October 3rd 19 at 02:03
the sensitivity of the human eye to different colors - alice_Swaniawski commented on October 3rd 19 at 02:06
Understood, thank you. - joanie4 commented on October 3rd 19 at 02:09
The most well-known formula (from Wiki): In the color spaces YUV and YIQ used in NTSC and PAL luminance Y' is calculated as follows: Y' = 0.299 R + 0.587 G + 0.114 B To account for the perception of the image by the human eye (sensitivity to green and blue color) in models of HDTV use the other indexes: Y' = 0.2126 R + 0.7152 G + 0.0722 B - Matt.Bashirian30 commented on October 3rd 19 at 02:12

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