There are some typefaces where this effect is taken into account, and there is a “white on black” font that is lighter in absolute weight than the “black on white” font.

In printed materials, type that is "reversed out" (white type on black) tends to close up and look thinner, especially in small sizes, so using a slightly bolder weight might be a good idea.

Reversed type is okay for headlines or short sections of text, but I wouldn't want to read long passages that way.

I think print versus screen might make all the difference here (but not sure).

hhp

Letters on screen are normally backlit, as opposed to printed letters. In some environments white on black will come out darker than black on white.

Viewed on a computer monitor is indeed different.

In conventional printing on paper, you'd normally create white type by printing a solid area of black ink that's knocked out where the letters appear, but as the ink is absorbed into the paper (especially on uncoated paper stock) the ink can spread a little into the white spaces making the type look thinner. On a monitor you don't have that problem.

True, it's the other problem: Light bleeding into dark, which is why light-on-dark signage is done with the lighter fonts Nick Shinn mentioned upstream.

Web/film people have all sorts of nicknames for it. I like 'glowtype' myself.

On screen white type is produced using all available colours, black is produced by switching all colours off... So much like you see a glow when you look directly at a light bulb or the sun (I don't advise this) relative to a dark background... Your white type will produce a slight barely noticeable halo of light making it glow - giving the appearance of bolder stronger text or a larger more punchy image.

The effect is completely reversed on printed material (as mentioned above) where the darker ink will bleed into the lighter ink or white area. For fine text it literally only has to be a tenth of a mm before it becomes noticeable to the naked eye. It can be made worse by auto trapping used in prepress software. A good prepress operator should warn you if you're going to have this issue and recommend ways around it...

Another technique for printing white type is to use foil stamping with a white foil. I've seen it used on brochure covers and business cards, and a cool thing is you can use black paper stock, so even the paper's edge is black. The business card below (not mine) uses 2 colors of foil — black and silver (but it could as easily been white).

But the technique is expensive and not used too often.

FF Transit
https://twitter.com/espiekermann/status/457041201032486914/photo/1