Enhancement request: remove or lighten background for carousel caption

The semi-transparent gray background that frames the title/description/button on the carousel sliders tends to detract from the photos appearing the carousel, especially when you have long-ish titles/descriptions. How can you make that background be more transpareent? Also, how can you eliminate that background completely?

I figured out how to reduce the amount of space the background takes with this custom CSS:
.carousel-caption {
padding: 1%;
}

But I’m not great at CSS/Firebug, and I can’t figure out how to “lighten” the background, or just eliminate it.