Should I use `pkg-config --libs opencv4` or `pkg-config --libs opencv`?

edit

Should I use

LDFLAGS+= `pkg-config --libs opencv4`
COMMON+= `pkg-config --cflags opencv4`

or

LDFLAGS+= `pkg-config --libs opencv`
COMMON+= `pkg-config --cflags opencv`

to compile my program with OpenCV?