"Stranger Things" cinematographer Caleb Heymann knew he was stepping into a big job when he signed on for season four. In fact, his schedule was as packed as the season's super-sized episodes."It was a solid 11 months where I was averaging about 90 hours of work a week, mostly on set," he tells CNBC Make It. "They're extraordinarily long hours that don't leave a lot of time for any sort of work-life balance." Heymann shot seven of the season's nine episodes. To get through the long days, he had to make sure to take care of his body. He stuck to an exercise routine, waking up before 4 a.m. three or four days a week to get a workout in, "even if I could only squeeze in 25 minutes."It was really important to keep my body healthy. Maintaining focus and energy levels over a long stretch like that, it's super grueling.Caleb HeymannCinematographer, "Stranger Things""It was really important to keep my body healthy," he says. "Maintaining focus and energy levels over a long stretch like that, it's super grueling."On top of staying fit, Heymann avoided eating too much from the on-set catering, and instead would meal prep for the week every Sunday. He would arrive to set each day carrying not only his camera equipment, but also a cooler containing his protein-packed salads.Cinematographer Caleb Heymann (right) on the set of 'Stranger Things' season four.Caleb Heymann"You want to be in control of the fuel that you're putting into your body," he says. "Even on a big production like ['Stranger Things'], the quality of ingredients and catering might not be the best. So taking control over what you're eating and what's going to be fueling you becomes very important to your stamina and your mental vitality."After leaving set, Heymann made an effort to not bring his work home with him. Though there was always more prep to be done for the next day's shoot, he made time to relax and "switch off" his mind with a glass of wine and some reading.But Heymann says that the fan response to the season — which last month became the second Netflix title to cross the billion-hour viewing mark — has made the whole experience worthwhile."It's been absolutely beyond anything that I could have ever imagined and made all those months of 90-plus hour weeks very much worth it," he says. "Seeing the reach of the show … it's really gratifying and humbling." Sign up now: Get smarter about your money and career with our weekly newsletterDon't miss: From 'Game of Thrones' to 'She-Hulk', here are 8 of the biggest shows streaming in August
How 'Stranger Things' cinematographer survived 90-hour weeks while shooting season four: 'It's super grueling'.