Olympus G.Zuiko Auto-S 40mm f/1.4 (PEN F)

Two millimeters separate this lens from the 38mm f/1.8 that shipped on most PEN F bodies, and that gap is the whole reason collectors hunt the 40. It is the faster, scarcer normal for Olympus's half-frame system. It gathers about three-quarters of a stop more light than the 38, it runs seven glass elements against the cheaper lens's six, and wide open it carries a soft, glowing character that fast normals of this era are known for.

The G in G.Zuiko is a count. Olympus coded element numbers by letter, D for four, E for five, F for six, G for seven, so the name alone tells you this is the seven-element design and not its six-element sibling. The layout is a double-Gauss, the standard recipe for a fast normal. At f/1.4 contrast drops, bright highlights bloom, and the background falls away smoothly behind a sharp subject. Stop down to f/2.8 or f/4 and it firms up into genuine cross-frame sharpness. People do not buy this lens for chart resolution. They buy it for how it looks open.

Remember it is a half-frame lens. The PEN F runs ordinary 35mm but exposes an 18x24mm frame, so the 40mm behaves the way a fast 58mm would on full-frame 35mm, a touch longer than normal, well suited to tight street work and head-and-shoulders portraits. Half-frame also gets you seventy-plus exposures from a 36-shot roll, so these cameras get shot loose and fast, much of it indoors in poor light. That is the case for the f/1.4 over the 1.8. Metering wide open in a dim room, you can lock Zone Light Meter to f/1.4 and let it solve for shutter speed.

The lens has a second life on digital. Adapt it to a Micro Four Thirds body and the small image circle covers the sensor with room to spare, giving you an 80mm-equivalent short portrait lens that keeps the old rendering. That demand, sitting on top of real scarcity, has pushed asking prices well above the 38mm f/1.8. You are paying for speed and character, not for resolving power.

The honest weakness is flare. This is single-coated 1960s glass, and a bright source near the frame edge throws veiling haze that flattens contrast fast. A hood helps, and keeping the light behind you helps more. The focus helicoids on surviving copies are usually due for a grease service, since sixty-year-old lubricant dries out and leaves the ring stiff or gritty. Buy one that has already been cleaned, or budget for a CLA. For available-light shooting on a small, beautifully made camera, it is the lens most PEN F owners end up wanting.