Lens “de-centering”?

I’ve come across this description in several posts, but I don’t understand what it means. Can someone enlighten me? Is there a simple way to determine this condition? Thanks in advance.

Thanks for the link!

I found those results rather weak, as the term ambiguous.


A decentered lens does not harm (Unless in a photogrammetrical camera. Or in combination with an extender, or the other way round)

What matters is is a decentered lens element, or even more of them.

Also matters a swivelled lens element. Which strictly speaking is not decentered, but in practice it may come together.

Also a tilted lens matters.