It is tempting to wonder whether the brass lenses that can sometimes be found at boot and jumble sales can be used with modern cameras. The answer depends on the camera as well as the ingenuity and dexterity of the user.
Brass lenses, which were traditionally fixed to baseboard cameras of old, often have neither an aperture ring nor the usual helical focusing mechanism. Aperture adjustment was achieved by inserting masks with different hole sizes into the lens via a small slot; focusing was normally by a rack-and-pinion system that moved either an entire section of the baseboard or just the lens itself within a tubular collar.
When mounting a brass lens on a modern camera, bellows provide both the necessary separation and the ability to change the distance to achieve sharp focusing. The forwards-andbackwards movement may feel strange at first but the same action was previously the norm for medium format film cameras such as the Mamiya RB67. Once practised, focusing in this way becomes reassuringly instinctive and surprisingly quick.
Low-cost bellows, of the type available through online sellers, often lack rigidity but are a good choice for mounting brass lenses when modification is required. A design where the lens mount is screwed in place, rather than being cast or riveted, is ideal as the same screw holes can be used to attach the new mounting plate, which can be something as simple as a step-up ring if the brass lens has an appropriate screw thread. A paper
