Olympus Zuiko Auto-Macro 50mm f/3.5

Half life size, not full, and that is the first thing anyone who has handled this lens will tell you. The 50mm f/3.5 Macro tops out at 1:2 on its own focusing helicoid, so to hit 1:1 you screw on the 25mm Auto Extension Tube (or put it on a bellows). The faster 50mm f/2 Macro that came later is brighter but still stops at 1:2 unaided, so it is no shortcut to full life size either. People hold the 1:2 ceiling against this lens. It is the wrong thing to fault it for. At 1:2 it is a genuinely sharp small SLR lens, and it fits in a jacket pocket next to a pen, which is more than you can say for almost any other macro fifty.

Olympus built it around floating elements, the first 35mm macro lens to use them, with a group that shifts as you focus to correct the aberrations that creep in at close distance. The optic is tuned for peak performance around 1:10, which is the working range it was meant for. Wide open at f/3.5 it is already crisp in the center, and as you stop down to f/8 it tightens up across the frame for copy work, flat art, stamps, leaves pinned to a board, though it carries enough field curvature that you want to mind the corners on a flat subject. Contrast is high in the Zuiko way, color leans neutral, and flare is well managed for a 1970s coating. The bokeh is not the reason you buy it. Out of focus areas are tidy and a touch nervous wide open, fine for a beetle, not what you want for a dreamy portrait background.

It belongs to the OM system, the line Yoshihisa Maitani designed to make a full SLR kit small enough to carry all day. The 49mm filter thread is shared across most of the standard OM primes, so one set of polarizers and NDs covers the bag. Stopping down past f/16 toward the f/22 minimum costs you sharpness to diffraction, the usual macro tax, so most people park it at f/8 or f/11 for real depth and stop there.

Who shoots it: scientists, dentists shooting clinical records, naturalists, anyone who needed a repro lens on a budget and a body that would not break their neck. This is a working tool, not a cult object, and it stays cheap because of it. Cross-shop it against the Nikon Micro-Nikkor 55mm f/3.5 and the two are spiritual twins, both half-life-size repro fifties from the same era, both excellent. The Nikon has the bigger system and the higher resale. The Olympus is lighter and usually a few dollars less.

One real limitation beyond the 1:2 ceiling: the f/3.5 maximum aperture makes the finder dim when you are nose-to-nose with a subject in low light, and the long focus throw is slow to rack. This is a tripod-and-patience lens, not a grab shot lens.

The exposure note that matters here is bellows compensation. As you extend toward 1:2 the lens moves far enough from the film plane that you lose real light, about a stop at half life size, and an in-camera meter on an OM body reads through the lens so it catches that automatically. If you are metering with a handheld or with Zone Light Meter, feed it the magnification and it computes the extension factor so your close focus shots are not a stop under. Forget it and your bug comes back muddy.