Blur Caption Background

Site URL: https://wisteria-panda-z2eg.squarespace.com/

pw: rotorrotor

Hello All,

I established these caption backgrounds from my fullscreen slideshow:

.gallery-caption {
  border-radius: 100px;
  background: rgba(0,0,0,0.73);}

I would now like to blur this caption background. However, I can't seem to target it. A simple filter: blur will blur the entire text along with it.

Can anyone help?

Best,

Gregor