An episode about positives, on a show called Negative Thinking.

Today I open a brand new drawer: our first Film Story, the biography of a material instead of a machine. And I'm starting with the film closest to my heart, the one with no negative at all. With reversal film, the very piece of film that sat behind your shutter develops into the finished photograph. No master copy in a drawer. A negative is a source. A slide is a survivor. You're holding the moment's only living witness.

That's why it shoots the way it does: about one stop of forgiveness, no fixing it later, because there is no later. Slide film is the sport played without a net. Its history is a whole century: Kodachrome, invented in 1935 by two classical musicians; National Geographic and family slide nights; the last roll developed at a small shop in Kansas at the end of 2010, part funeral, part pilgrimage. And the survivor in my bag today: Fujichrome Provia 100F, the honest one, fine-grained and faithful. My first film ever was positive film by pure chance. It was Nakahira's exhibition that turned the accident into a choice. The film with no negative demands the most negative thinking of all.

Your move this week: make one frame with no net. Decide everything before you shoot, lock the exposure, take one single frame, and vow: no retake, no edit, no crop. What comes out is the photograph, forever. No camera? Ask someone a generation up about slide night, and what the projector sounded like. You'll watch a wall light up behind their eyes.

Coming Saturday: I finally pay a debt from episode one. The roll every one of us shoots exactly once. The first one.

I'm Dan. This has been Negative Thinking. New episodes Wednesday and Saturday. Follow wherever you listen.

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