Based on the available evidence, the “Adam-Salomon style” appears to be essentially Rembrandt-style lighting in the broader, classical sense: strong directional light used to model the face with dramatic light and shadow (chiaroscuro). It is not necessarily a separate modern lighting pattern with its own distinct marker.

The key idea is sculptural form. Adam-Salomon, who had a background as a sculptor, used lighting to emphasize three-dimensional facial structure. In that sense, his approach overlaps with what we now call Rembrandt lighting, though not always the narrowly defined version that requires a perfect triangle of light under the eye.

To recreate the look:

• use a single dominant side light placed high enough to create depth and shadow
• aim for strong chiaroscuro rather than flat, even illumination
• pose the subject formally, inspired by classical portrait painting or sculpture
• use rich, dark, luxurious materials such as velvet for wardrobe or backdrop
• for a more historical feel, present the image in black and white and avoid an overly clinical modern look

So the “special technique” was likely less a unique named setup and more a painterly, sculptural use of directional light, pose, and styling.