Is Night Mode in iOS really sight-friendly?

I am pretty used right know to reading things on dark backgrounds and I feel that my eyes get less tired than with regular white backgrounds, especially while programming or basically any activity that involves hours looking at the screen.

My question is, on iPad and iPhone, how does Night Mode really work?
I mean, does it iluminate the black pixels on the screen, or does the OS keep them off so that your eyes receive the less amount of light possible?

It could seem to be a little silly, but for me is very important as I use this device for reading a considerable amount of time.

While the display's backlight is always illuminated, a black pixel is blocking nearly all the light from behind it so that in effect your eye does receive much less light. In this case, if you find reading with dark backgrounds easier then Night Mode will be helpful. What you don't get is any energy savings.

The black pixels are still illuminated by the backlight. The display's architecture does not facilitate only providing backlight to lit pixels, unlike OLED or similar.