My current apartment has them. They're far less effective than the worst-installed blackout curtains. When pulled down fully they block maybe.. half the light?

My current apartment has them. They're far less effective than the worst-installed blackout curtains. When pulled down fully they block maybe.. half the light? Blackout curtains themselves do a good job, but have a lot of side bleed. Blinds even out the problem by.. also adding side bleed between each of the sheets.