Changes to Cover Photo Appearance

Hello! Is there a way to set the "text contrast" for the cover photo to 0? It seems like 10% is the lowest setting, but at 10%, the whites in my very-carefully-crafted cover photo come out gray. I'm familiar with CSS, but I can't figure out what class is controlling that setting? Anybody out there have any suggestions on this?

Frustrating how many style settings in Rise we have zero control over. . . 

Thank you!

--Meg