The Smallest L-mount Setup

Sometimes it’s tricky to have a compact full-frame with a decent prime. But is that really true?

Here is a setup that seriously challenges that idea.

Sigma FP L + Pentax DA 40mm F2.8 XS

At the center of this setup is the Sigma FP L. Even by full-frame standards, it’s an incredibly compact camera. But depending on the lens you choose, it can feel like a completely different machine.

The lens here is the Pentax DA 40mm XS, one of the thinnest prime lenses ever made. It’s often called a pancake lens, but this one is more like a sheet of metal with glass inside.

The Aperture Problem

There is one catch. This is an AF lens designed for Pentax, which means there is no aperture ring on the lens itself.

Mounted directly, you wouldn’t be able to control the aperture at all. So an adapter is essential.

K&F Concept PK DA–L Adapter

I’m using the K&F Concept PK DA–L adapter, which comes with a built-in aperture control ring.

There’s no electronic communication, but the physical aperture control solves the problem beautifully. In fact, it makes the whole setup feel refreshingly simple and manual.

Turning the aperture ring feels direct and mechanical — there’s something satisfying about knowing exactly how much light you’re letting in.

The aperture stopped down

The lens wide open

Size Is the Point

This is where the setup really shines.

With the adapter and lens combined, the total protrusion from the camera body is about 3.3 cm (about 1.3 inches).

A full-frame L-mount camera with a 40mm prime, and it barely sticks out at all.

It slips easily into a bag, and when carried, it feels less like “bringing a camera” and more like carrying a small, thoughtfully designed object.

Final Thoughts

No autofocus. No electronic aperture control. EXIF data isn’t out there.

But this setup offers something numbers can’t fully describe. Calling it “The Smallest L-Mount Setup” doesn’t feel like an exaggeration, it feels like an honest description.