'ls' name and 'ls | grep name' different

Bonjour,

I explain  it as simple as possible:

:;  set | egrep 'LC_A|LANG'
GDM_LANG=fr_FR.UTF-8
LANG=fr_FR.UTF-8
LC_ALL=fr_FR.UTF-8
SLIM_LANG=fr_FR.UTF-8

:;  ls -i  1989* ; ls -i | grep 1989 ;  ls -ib  1989* ; ls -ib | grep 1989
9920 1989 Amn*??*sia.mp4
 9920 1989 Amn*é*sia.mp4
9920 1989 Amn\303\251sia.mp4
 9920 1989 Amn\303\251sia.mp4

We see that with ls only the accent is transformed into ??
And this is not the case with the pipe followed by grep

I don't see an explanation since the pipe should not modify the ascii stream
especially not by correcting the flow!

Au secours !
Bien cordialement