This is a very fast manual focus, manual stop-down, telephoto prime lens, made in Japan by Sigma.
It has a Sigma Y/S (Yamaki System) mount, which very similar to the T2 mount and this allows it to be used on lots of different cameras simply by using one of the many different Y/S mount adapters that are available..
Its a Sonnar type optical design so its bokeh quality is very good.
The Sigmatel has a 77mm filter thread, making it slightly more compact and easier to hold in the hand than similar lenses, like the Porst and Spiratone versions, which have a 82mm filter thread.
Wide open it has fairly low contrast but CA is well controlled and the DOF is very shallow.
Its best between f4 and f5.6 where its pin sharp and has excellent contrast.
Because of its large and exposed front element it is recommended that it is used with a deep lenshood on it at all times as this helps to maximise its contrast at all apertures and also prevents flare from the Sun or other very bright off-axis light sources.
Specs: It has 6 Elements in five groups, an 8 blade Iris and weighs about 800g. The dimensions are Length = 100mm @ infinity, 112mm @ MFD and the Diameter = 80mm.
The Minimum Focus Distance (MFD) is about 4 foot 3 inches (or about 1.33m).
BTW, "Multi Scalematic" refers to the strange "vertical" and "horizontal" measurement scales which can be seen on the lens barrel, in front of the conventional focus scale. What these are used for is unknown, but to me it looks like the scales refer to the width and height of what you see through the viewfinder at different distances from the film plane. I.e. if you're focusing at 60 ft, the plane in focus will be a bit less than 5 ft wide and a bit more than 3 ft high.
Scan of
sigma brochure here.
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