Vivitar Automatic 2x Tele Converter for M42 Mount

The Vivitar Automatic 2x Tele Converter for M42 Mount is a third-party accessory designed to double the effective focal length of a compatible M42 screw-mount lens, giving photographers extended telephoto reach without purchasing a longer prime or zoom lens. As a Vivitar-branded product, it was marketed as an affordable option for photographers using M42-mount cameras during the film SLR era, a mount standard widely shared across brands including Pentax Spotmatic-series bodies and numerous other M42-compatible systems.

The teleconverter mounts between the camera body and a compatible M42 lens, optically doubling the focal length of whatever lens is attached, for example turning a 50mm lens into an effective 100mm, or a 135mm lens into an effective 270mm. This offers a low-cost way to extend telephoto reach for wildlife, sports, or distant subjects using lenses already in a photographer’s kit, rather than investing in additional longer glass. The “Automatic” designation indicates the teleconverter maintains automatic aperture functionality with compatible M42 lenses, allowing the diaphragm to continue operating automatically as it would without the converter attached, rather than requiring manual stop-down metering.

As with any 2x teleconverter, using this accessory comes with a light loss of two stops, meaning the effective maximum aperture of the attached lens is reduced accordingly, for example an f/2.8 lens becomes effective f/5.6 once the converter is attached. This tradeoff affects viewfinder brightness and how much light reaches the film, and is more pronounced with 2x designs compared to smaller 1.4x converters.

As a fully manual accessory consistent with the M42 screw-mount system it’s designed for, the teleconverter has no autofocus or electronic communication beyond the mechanical aperture coupling, requiring photographers to focus manually as they would with any M42-mount lens. Because Vivitar produced third-party teleconverters across multiple lens mounts and occasionally varying optical formulas, photographers should confirm the specific optical construction and condition of this individual unit, since image quality and sharpness with any teleconverter depend heavily on both the converter and the quality of the lens it’s paired with.

Key Features
– 2x teleconverter for M42 screw-mount lenses
– Maintains automatic aperture function with compatible M42 lenses
– Doubles effective focal length of attached lens
– Two-stop light loss (e.g., f/2.8 becomes effective f/5.6)
– Fully manual focus operation (consistent with M42-mount system)
– Third-party construction typical of the film SLR era