One-sided planes.. are double sided

[Ajani]

I have set up some plains for reference images. When I spin the viewport around, instead of the back being see through, all I can see is a black polygon. This is really annoying, does anyone know how to turn this off?

[Dicko]

Right click on your object and select properties then turn on Back Face Cull.

[Aurelius]

I think it's because backface culling is off by default to speed things up. You can change the setting by going to customize > preferences > viewport configuration.