Nikon PK-13 AI Auto Extension Tube
WHAT CONDITION THE CONDITION IS IN: 88-Day Confirmed Operation Warranty. Clean and pristine. Some minor wear marks, only noted for full disclosure. Scroll down if you want to learn about the design, performance, and story behind it. Or don’t. It’ll be here either way.
The Nikon PK-13 is a 27.5mm extension tube. It is all-metal, glassless, and constitutionally unbothered by trends. It arrived as part of Nikon's AI system, adding the mechanical coupling that let cameras meter wide open. This was a civilizing upgrade over its predecessors, though it would never brag about it.
It's officially archived, which is the corporate way of saying retired. Except nobody told the PK-13, because it's still the tool of choice for anyone scanning 35mm film at true 1:1 life-size. Paired with a 55mm Micro-Nikkor that can't quite get there alone, the tube provides the missing 27.5mm of ambition.
There's no glass inside, so image quality remains entirely the lens's responsibility. You'll surrender two stops of light at full magnification, which is, as with most things worth doing, a fair trade. It plays beautifully with AI, AI-S, and AF-D lenses. It has no patience for G or E-types without aperture rings, and one suspects the feeling is mutual.
The working distance at 1:1 is a mere five centimetres. That's close enough to make lighting genuinely difficult, which is the PK-13's way of reminding you that intimacy always comes with complications.
This particular example wears its years lightly, lettering still crisp, which feels right for something that was built not to impress, but to endure.
