While the Robots were capable of sequence photography, the shutter that made this possible placed some constraints upon taking lenses and shutter speeds. To reach speeds as high as 1/500 second the inertia of the thin vulcanite shutter disc had to be kept at a minimum, requiring a small-diameter disc with a minimal sector opening. The screw in lens mount was 26 mm in diameter. The clear lens opening was only 20 mm. In contrast, Leica's mount was almost twice as large at 39 mm. Further, to permit lens interchangeability, the shutter was mounted behind the lens so the disc interrupted the expanding light cone. This placed some limits on lens design. While the 75mm Sonnar could be used with the aperture set to "f/"22, the Tele-Xenar suffered from some shutter disc vignetting unless opened more.