Mathieu Stern spotted an oddity one afternoon at a French flea market. Inside a simple blue canister sat a compact Foth 50 millimeter f 2.5 lens from the late 1920s. Three euros later it was his. The optic had come from a Foth Derby folding camera built for 127 roll film, a model once positioned as a rival to early Leica designs. It even showed up in a few motion pictures from that period, including work tied to Alfred Hitchcock.
Mathieu considered rehousing this lens in his Sony FX3 movie camera, which has a quite thorough 4K full frame sensor. The problem was that the lens itself lacked both aperture control and a proper focusing system, which had been missing for years and had long ago vanished. Early experimentation involved using a bizarre elcoid adapter with an added bit of aperture stuck just behind the elements, and while this should have given Mathieu plenty of light control in theory, it ended up introducing heavy vignetting in practice, simply because the lens barrel was a little too narrow to accommodate the setup comfortably.
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He then tried another approach, using a Fotodiox macro adapter developed for use with Sony E-mount cameras. This useful piece of equipment contains a built-in helicoid for focus adjustments, as well as a clever drop-in slot for accepting neutral density filters when necessary. This combination resolved both the exposure and focusing difficulties in one step. On bright days, the filters helped keep objects from blowing out, and the helicoid allowed him to dial in sharp focus down to 30 cms or even 20 cms when he ventured into macro photography.
Once he had the lens fitted and balanced, he could truly put the camera through its paces. He began framing everyday scenes and letting the vintage lens do its thing. Sharpness was rather amazing in the center of the frame and across the sensor, but as you approached the edges, the image softened in a gradual, fluid manner that naturally leads the attention to the topic. Out-of-focus highlights become a gentle swirl rather than the overly convoluted jumble that is so common with current optics. Uncoated glass parts disperse incoming light somewhat, giving bright regions a subtle, warm glow that feels alive rather than cold and sterile.
The low light clips were really impressive. The fast f2.5 aperture, along with the FX3 sensor, handled low-light circumstances with ease, without injecting any unwanted high ISO noise into the image. The color reproduction was beautiful and deep, similar to what you’d expect when discussing archival footage. Mathieu equated the experience to having a window into the past while continuously filming the present. He processed the clip in Adobe Premiere Pro and added a few of his bespoke LUT packs to adjust the tones somewhat. The final clips have a distinct flavor that makes modern zoom lenses appear drab in contrast. People watching the results frequently pause and repeat key sections to have a better look at how the light falls and how backgrounds fade away.
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