I first met Steve Jobs on a photo shoot for TIME in 1982. I had no idea that he was going to be my friend or that he was going to be this incredible genius — a part of all our lives, in what we do and what we see. He was speaking to a group of Stanford students in a dorm living room, and it was hard to photograph him there and not be in the way. You had to have light, and I was creeping around. But he was game. I asked him to stand on top of an Apple sign, and he did it. I asked him to stand in front of an Apple cutout (which ended up on the cover of Fortune magazine), and he did that too. I thought, This is you. This is who you are.

He was so much fun because he was so quick — he was such a fast study. You showed him anything and he could get it in a second. I was always fascinated by his design sense. It was wonderful because he liked my pictures.

I really will miss his inventiveness, his ideas, his eyes — and how bright he was all over. He had some kind of electricity about him. He was very, very focused in the office. He demanded a lot of the people who worked for him. I’m sure Steve wasn’t the easiest person to work for, but what a fascinating person to work for.

Diana Walker was TIME’s White House photographer for 20 years, where she captured intimate moments with five Presidents.