I should have mentioned that I was thinking of a sheet of paper in the same room / with the same lightning, next to the screen we are speaking about. Otherwise, yes, indeed.
> why not just support different contrast levels
So what I understand from this is that we can't get this right (in HTML/CSS) for now because we don't have details about the environment of the user wrt lighting/contrast (preferences/perception).
It seems like something that should be fixed at the browser or the OS level. One should be able to say: "this is some black text on white background that needs to be displayed so as to be comfortable for the user given their environment" (or something). Maybe that needs to be the default by the way.
Until then, any forced value is going to suck for someone.
Advanced configuration could allow you to tune the curve continuously (or in a sufficient number of discreet steps that it seems to be continuous).
I think I noticed my Android phone at least doing a "I'll remember a relative brightness you want for this much light outside", though I haven't checked if it's really that.
Adapting to the ambient light and reading on paper which is never more than 90% DIFFUSE reflectance (typically 80% for paperbacks, and 70% for newspaper) is not at all like having polarized light beamed straight into your ocular medium to collide with your retina at well over 100% of the ambient adaptation level. Or words to that effect.
> _There is such a thing as too much contrast._
Yes, there is absolutely such a thing as too much contrast, however, I hesitate to say this as it is so often misunderstood—spatial frequency is the key factor to determine first. The contrast needed for small thin body text is very different than that needed for a large bold headline.
The thing that some find confusing is thinking that too much contrast with a light background means making the small thin text lighter grey, when in fact the text should stay darker tha #303030, and lower the luminance of the background to #e6e2dd. I say as much in the article.
There is such a thing as too much contrast. Typical ergonomic workspace regulations (like the ASR in Germany for example) will tell you how much contrast any given type of workspace environment should have between the brightest and the darkest point for a reason.
Now someone with an old, washed out TFT might get a much different contrast when viewing a #000 #FFF page of text than someone with a modern HDR display if this is not accounted for in software. Now you could say they need to adjust their screen – but text is not the only thing people view on screens. Why would you throw away image and color fidelity, because some website doesn't fit that setup? We are on computers, why not just support different contrast levels like we do with dark mode?
--- ¹ except maybe black holes