Is Panasonic's $400 Lumix S 40mm f/2 Worth It?

At $400, the Panasonic Lumix S 40mm f/2 is one of the least expensive ways to put an official autofocus prime on an L-mount body. A 40mm sits between the standard 35mm and 50mm choices, and a lens this small and cheap has a good chance of becoming the one that never leaves your camera.

Christopher Frost paired the Panasonic Lumix S 40mm f/2 with a Panasonic Lumix S1RII and its 44-megapixel full frame sensor, a demanding match for any budget lens. The lens weighs under 150 g, yet it doesn't feel cheap in the hand. You get a metal mount with a weather-sealing gasket, an autofocus/manual focus switch, and a plastic focus ring that turns smoothly and responds precisely when you focus by hand. Focus breathing is low, so you can pull focus during a video clip without the frame visibly shifting. Autofocus is accurate and nearly silent, though only average in speed. There's no optical stabilization, and the lens worked well with the camera's in-body stabilization anyway.

Wide open, the center of the frame is already very sharp, with somewhat soft contrast. By f/2.8, the center is close to perfect, and at f/4, it gets there. The corners are a different picture at f/2. They look hazy, with coma showing up as a likely cause, although fine detail survives under the low contrast. Stopping down to f/2.8 helps a lot, and from f/4 the lens is sharp from corner to corner, holding that level until diffraction starts to soften things at f/11. With corrections switched off, distortion is almost perfectly controlled in the optics themselves, which is unusual at this price. Vignetting is heavy at f/2 and drops off sharply by f/2.8 or f/4.

The diagonal of a full frame sensor measures about 43mm, and that figure is the textbook definition of a "normal" focal length. A 40mm lands closer to it than either a 35mm or a 50mm, which explains why Frost describes the view as close to the human eye. You get a touch of wide angle context around your subject without the stretched edges of a 28mm or the tight, isolating feel of a longer lens. Other systems have leaned into the same idea with compact, moderately fast primes: Nikon has the Nikon Z 40mm f/2, and Sony offers the Sony FE 40mm f/2.5 G. Each of them trades the size and price of an f/1.4 for something you'll actually carry every day. A lens like this suits street work, travel, family photos, and documenting your own life, where you want people and their surroundings in the same frame. If you can't decide between 35mm and 50mm, shoot a week with both and crop the 35mm files to 40mm. You'll learn quickly whether the in-between view fits how you see.

Close focus sits at 30 cm, a usable distance for a lens with this field of view, but performance up close depends heavily on aperture. At f/2, close-up shots look poor. At f/2.8, detail improves a great deal, along with a lot of blue color fringing, and by f/4, close-ups look excellent. Bright lights are a weaker area, with plenty of flare and glare showing up in Frost's tests. No hood comes in the box, and the lens has no bayonet to mount one later, so the 62 mm filter thread is the only attachment point on the front. Night shots of point light sources in the corners show the coma clearly at f/2, and the sunstar, bokeh, and longitudinal chromatic aberration results add more detail on how the lens behaves at different apertures.

Frost's full set of sample frames, from the night corners to the busy-background bokeh shots, is waiting in the video above.