Voigtlander Ultron 35mm f/1.7 Aspherical (VM)

Most people meet this lens on the way out of the Summicron aisle. Leica's f/2 Summicron-M is the reference 35, and it costs three or four times what Voigtlander asks for the Ultron f/1.7. You give up the red dot and a chunk of resale value. You keep a lens that is roughly half a stop faster and, on most negatives, hard to separate from the Leica in a print.

History first, because it gets garbled. The original aspherical Ultron 35/1.7 arrived around 1999 in L39 screw mount, riding the Bessa revival that brought screw and bayonet rangefinders back. The lens reviewed here is the VM, the Leica M-bayonet version Cosina put out later (2015) as a fresh optical design with improved glass and coatings. The Ultron name itself goes back well before any aspheric glass. It traces to A.W. Tronnier's modified double-Gauss work from the 1950s, first seen on the Ultron 50/2 for the Prominent. The "Aspherical" on the barrel is the modern suffix, not the source of the name.

Wide open at f/1.7 it is sharp in the center with the edges trailing a little, which is normal for a fast 35 of this class. Stop to f/4 and it bites corner to corner. Contrast sits a notch below current Leica glass. On Tri-X I get open shadows and midtones that do not clip, so the negative scans on the flat side and takes a contrast grade without fighting back. Some people read that as low contrast; I read it as headroom.

Bokeh is the honest weak spot. At f/1.7 out-of-focus highlights can carry a faint outline, and foliage behind the subject goes a touch busy. At 35mm this was never going to be a portrait creamer, and that is fine for what it does. It is a street and documentary tool. The speed is there so you can shoot a dim cafe on Tri-X at 1/30 handheld, and the short barrel vanishes on a small body in a way the bigger Leica primes do not.

Flare is controlled but not bulletproof. Point it at a streetlight and you may catch a small veil; a hood handles most of it. The 46mm filter thread is common, so a yellow contrast filter for black and white or an ND for daylight wide-open work is cheap to add. If you run a strong ND, meter through it or dial the correction in. In Zone Light Meter you set the filter factor once and the reading already accounts for the lost stops before you touch the aperture ring.

Who buys it now: rangefinder shooters who want a genuinely fast 35 for low light and street and do not have Summilux money. The cross-shop is the Summicron above it (more contrast, more cash) and, on the slower side, the Cosina-made Zeiss C-Biogon 35mm f/2.8 ZM, which runs flatter-field and more clinical. The Ultron sits between them. It is gentle wide open and proper sharp stopped down, and it is small and cheap enough that it actually stays in the bag after the next body purchase clears out the expensive glass.