Want no screen saver

I have an iMac, 5K retina, 1 TB running Mojave 10.14.2. Previously, when it went into sleep mode I would have a blank black screen ... no screen saver. I was in system preferences today looking at screen saver options and changed to a photo. I want to go back to a blank screen, but there's no option for that within screen saver. How do I simply have a black screen as my screen saver? Thanks.