Greyscale colour model

The greyscale colour model has a colour space composed of a range of shades of grey without apparent colour.
The darkest possible shade of a greyscale is black and the lightest is white.
But a  greyscale is not a simple series of perceptually even steps between black and white.
A greyscale retains the brightness of the original hue.  So yellow is a very light hue whilst blue is a very dark hue.
A greyscale renders the relative saturation and brightness of different colours with their hue removed. So changing a colour photo to greyscale creates a black-and-white version.
Any range of colours within the RGB additive colour model or the CMY subtractive colour models can be converted to greyscale colour mode.
RGB colour model – If 1530 fully saturated RGB colours are converted to greyscale then brightness percentages between 11.00% and 89.00% two decimal places
Red = 70%
Orange  = 40.38%
Yellow = 11%
Green = 41%
Blue = 89%
Violet = 74.06%
HSB colour model
Either: Hue = 0, Saturation = 0, Brightness =  11.00% (Yellow) and 89.00% (Blue)
Or if the aim is to switch back to the original hue then Hue = 00 to 3590, Saturation = 0, Brightness =  11.00% (Yellow) and 89.00% (Blue)
Any greyscale without a corresponding RGB or HSB value can be represented by matching rgb values ie 178, 178, 178 corresponds with cyan
Greyscale images are also known as black-and-white or monochrome images and are composed exclusively of shades of grey, varying from black at the weakest intensity to white at the strongest. A greyscale image shows natural colour luminance with hue and saturation removed and so it carries only intensity information.
  • Greyscale images have many shades of grey in between black and white.
  • Greyscale images are distinct from one-bit bi-tonal black-and-white images which, in the context of computer imaging, are images with only two colours: black and white.
  • Greyscale images can be the result of measuring the intensity of light at each pixel against a selected wavelength or a weighted combination of wavelengths. In this case, the selected wavelengths can be from anywhere within the electromagnetic spectrum (e.g. infrared, visible light, ultraviolet.).
  • A colourimetric (or more specifically photometric) greyscale image is an image that has a defined greyscale colourspace, which maps the stored numeric sample values to the achromatic channel of a standard colour-space, which itself, is based on measured properties of human vision.