TLS Mamiya 645 inc. Speed Booster LPL Mount 17mm t3.3

17mm t3.3

The Mamiya 645 rehousing project is a unique venture for TLS so far. It was decided to offer the Mamiya 645 Sekor C lenses as both a standard rehousing, but also with the option of a built-in speed booster. Both versions of the rehousing have 95mm fronts as standard. The original lenses were designed to cover a film area of 6cm x 4.5cm, this means that the lenses all cover the Alexa 65 sensor and the New Arri Alexa 265 sensor as standard. However, rehousing them with the built-in speed booster still allows the lenses to cover all full frame sensors, including LF open gate, while improving the speed of the base lens by one stop. The Mamiya 645 Sekor C lenses were developed during the 1970s and released during the second half of the decade. The lenses boasted a multi-layer coating and sharp, clean optics from corner to corner. They produce smooth out of focus areas and are well matched across the focal lengths. These lenses provide a bridge between the classic ‘vintage’ look and modern optical designs and coatings that manufacturers produce to date.

Speed boosting a Mamiya 645

The speed booster is essentially a 0.71x adaptor that sits at the rear of the original base lens. Therefore, it works by concentrating the light transmitted through the lens, onto a smaller surface area than it was originally designed for. This has two major benefits for the Mamiya 645 lenses. Firstly, it increases the speed of the lens by one f-stop. An original lens with an aperture of f2.8 becomes a rehoused lens with a T stop of T2.3/f2 (remember that f-stop is a formulated amount of light whereas T-stop is actual light transmitted through the lens). Not only this, but it reduces the focal length of the lens as well. Therefore, a 35mm base lens becomes a 25mm once rehoused with the speed booster.

The beauty of this combination is the effect it has on the optical performance of the lens. Introducing the speed booster to these lenses adds a soft fall off towards the edges of the frame. Therefore, the speed boosted lens renders a beautiful cinematic characteristic not seen in the original lens. As the speed booster is built into the rehousing, it is unnoticeable from an aesthetic point of view too.