Carl Zeiss Planar T* 45mm f/2 G

People who call this the sharpest normal lens ever put on a 35mm camera have usually shot the Leica Summicron right beside it and watched it lose. The Contax G Planar 45mm f/2 resolves to the grain wide open. Not good for an f/2. Better than most lenses are at f/5.6. Without an SLR mirror box dictating a long back-focus, Zeiss had room to place the rear group where the optics wanted it, and they set it a deliberate distance off the film plane so the body's TTL actual-aperture metering would read the exposure accurately. Freed from a mirror box, the double-Gauss layout stays compact and tightly corrected.

The formula is a Planar, the double-Gauss design Zeiss has refined since Paul Rudolph drew the first one in 1896, here a six-element modified version with T* multicoating. At f/2 the center is already biting, contrast is high, and the microcontrast separates planes the way good Zeiss glass does. Stop to f/4 and the corners come up to meet it; by f/5.6 the whole frame is uniform and razor-flat. Bokeh is the trade. This is a high-resolution, high-contrast optic, not a soft one, so out-of-focus rendering is competent rather than creamy, and backgrounds can run a little nervous when there are hard edges behind the subject. Field curvature is well controlled. Flare resistance is excellent, and rendering runs cool and saturated.

It was the standard lens of the Contax G1 and G2, the autofocus rangefinder Kyocera built in the nineties for people who wanted Zeiss rendering in a body smaller than an SLR and cheaper than a Leica M. Travel shooters, documentary photographers, anyone who valued a compact kit that out-resolved almost everything on the market reached for this first. A normal lens that prints like a much more expensive one.

The honest weakness is not the glass. It is the focusing. The G1's passive AF is slow and hunts in dim, low-contrast light; the G2 added active infrared assist for close, low-contrast subjects but still misjudges scenes at f/2 where the thin depth of field is unforgiving. You cannot reliably manual-focus it either. The body's focus wheel is awkward and there is no real rangefinder feel. You are trusting the camera, and at full aperture up close that trust gets tested.

Today it sits in an odd spot. The G system is dead and Contax is gone, but the optics are good enough that people keep it alive on digital. It won't natively mount on a modern camera, but current adapters keep it working: Funleader's G45-to-Leica-M conversion, Shoten's Contax-G AF adapters for Sony E and Nikon Z, Techart's TZG-01 for Nikon Z, some with autofocus. That is why people pay to put that 45mm rendering on a sensor. It cross-shops against the 50mm Summicron and adapted Zeiss ZM glass, usually winning on resolution and losing on focusing experience. When you do shoot it wide open in low light, where the AF struggles most, meter off the subject in Zone Light Meter and place the shadow where you want it rather than trusting an averaged reading. The 46mm front takes a small ND if you need to hold f/2 in daylight.