Simple: How to add Featured image credit line

Hello everyone. I want to be able to add a simple credit line on the bottom right corner, or in small faded text below, my featured images for posts. The plug ins I’ve tried for this problem have large captions that don’t look visually appealing and I wanted to know the best way to do this.

Basically I want to be able to give credit (link, photographer name, etc) but not have it be a big attention grabber.

I’m using the ColorMag theme for reference.

Thanks for any help!