sRGB gamma is often approximated to 2.2 [1], but the actual function has a linear section near 0, and a non-linear section with gamma of 2.4, possibly to avoid numerical difficulties near 0.

The document you cite claims that CRT gamma is typically between 2.35 and 2.55.

Human eye gamma can probably be approximated with cieLAB, that is designed to be a perceptually uniform colorspace, which seemingly has a gamma of 3 [2], although it also has a linear section, so maybe slightly lower overall gamma. ciaLAB is not state of the art though in perceptually uniform colorspaces.

[1] https://en.wikipedia.org/wiki/SRGB

[2] https://en.wikipedia.org/wiki/CIELAB_color_space

What I don't like about this whole CRT/gamma topic:

1. It brings in perceptually uniform colorspaces to the discussion, while it's completely unnecessary. Perceptually uniform colorspaces are mostly unsuitable for arithmetic on colors like any other non-linear colorspace.

2. While the sRGB colorspace and a colorspace defined by a CRT monitor's transfer function are closer to perceptually uniform than a linear colorspace, they are still pretty damn far from it. sRGB still does a decent job to prevent banding in dark areas.

3. The sRGB colorspace is not identical to a colorspace defined by a CRT monitor's transfer function.

4. "gamma" is a crude approximation for transfer functions, assuming they follow a power function on all of their domain.

5. This whole thing about CRTs and gamma doesn't matter if you just want to understand that if you want to do arithmetic on color components, then you most probably want it represented in a linear colorspace (didn't even talk about it yet), and most color values you encounter is actually encoded in sRGB, so you want to convert that to linear first, then convert the result back, depending on what your output requires. This is the most widespread bug in computer color and you don't need the history of CRTs to do that, and in fact this has nothing to do with perceptually uniform colorspaces.