Honestly, Kon didn't care whether or not they kept the light on. He was a Super. No one had eyesight like a Super - excepting other Supers, of course.
But even though Kon didn't care, he'd fully expected that Tim would want to do this in the dark. Tim was a Bat down to his core; Kon could count on one hand the number of times he'd seen Tim do something in the light of day and look like he'd actually enjoyed it.
The confusion must have shown on his face. "What's the matter?" Tim asked, entirely too anxiously for Kon's comfort. Mostly because that anxiousness made Tim's hands stop the rather fantastic stroking they'd otherwise been occupied with.
"You stopped. Don't stop!"
"You looked upset," Tim pointed out, and Kon sighed. That was Tim's analytical face - the one that would always be "Robin's" face, no matter how much Tim wasn't Robin anymore.
Tim would always be Robin, to Kon.
"I'm not upset," Kon argued. "I'm just surprised that you want the light on."
Tim grinned sheepishly. "I've wanted to do this for a long, long time," he said softly. "And then you died."
"Man, I keep apologizing for that -"
Tim placed a finger on Kon's lips. "You don't have to apologize. I just don't have Kryptonian sight. I need all the lights on, because I want to see everything. Unless you want me to wear my cowl, which has night lenses built into the cowl..."
"Tim, buddy, I am all for costume play, if that's your kink, but not with that hideous Dr. Mid-night looking thing you stole from Jason Todd."
"I didn't steal it from Jason! He threw it away!"
"Details, Tim. Specifically, details I don't care about." Kon reached up and ran his fingers through Tim's still too-long hair. He was kind of getting used to it. "What do you say we get back to the details I do care about?"
"Sounds like a plan," Tim said, and then he smiled.
It was a rare and wonderful sight, these days, and Kon had every intention of making sure that smile stayed in place for the rest of the night.
Or at least until they wore each other out.