need to increase contrast in all emacs faces for legibility

[Samuel Wales <samologist@gmail.com>]

at night, i need much more contrast in my emacs faces in order to
increase legibility.

during the day i want the same faces i currently have.

is it possible to programmatically increase foreground contrast
against their background in all faces?

i already have the background black or close to it.

i have heard that in practice, it is not a question of just increasing
brightness.  there is an accessibility website that can calculate it
but i don't know the url.

but even if nobody knows the theory of contrast perception, or
whatever applies here, even just increasing foreground brightness of
all faces would probably increase legibility.

thanks.