NFL teams usually have their team logo painted in the middle of their home field on the 50 yard line.
I've noticed that some stadiums are missing the logo and instead have the NFL logo printed at the center of the field. Carolina Panther's Band of America Stadium and and New Jersey's Metlife Stadium are 2 examples. The latter hosts both the New York Jets and New York Giants. Since 2 teams play at Metlife Stadium I'm assuming the NFL logo is used to keep the field neutral.
Which NFL stadiums have the NFL logo at the center, and what's the reason behind this?