The Gen II 25-250 mm HP T3.7 is an approx 1980s vintage lens. An optical improvement. Came in Arri bayonet or Arri PL lens mount. HP stands for High Performance.
The HP unit was introduced in approx. 1986-87 in response to Cooke's dominance of the professional cine zoom market. I believe it shared aspects of its optical design with the older, traditional Angenieux 10x25B f3.2/T3.9 zoom, with the following improvements:
Entirely new mechanical unit. Partial internal focus: Front end tracked in and out during focusing, but did not rotate. Front ring had rectangular mask like the Cooke.
Redesigned front end, better wide angle performance. New glass types used, same glass as the HR which cost about $20,000 used.
All elements coated with new Angenieux HEC (high efficiency) multi-layer anti-reflection coatings. These dramatically increase flair rejection & contrast and decrease veiling glare (image de-saturation) and transmission loss. You get a higher T-stop (Transmission stop) for the same geometric aperture.
The same f3.2 iris now delivers T3.7 instead of T3.9. This is an amazing rare and fast professional cinema lens. When is comes to lenses, condition is everything!
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