The Vivitar Auto 135mm f/3.5 is a classic telephoto prime lens known for its solid build and optical performance. Here are some detailed features and specifications:

Key Features:

Focal Length: 135mm

Maximum Aperture: f/3.5

Minimum Aperture: f/32

Lens Construction: 4 elements in 3 groups

Diaphragm Blades: 6

Filter Size: 52mm

Minimum Focus Distance: 1.8 meters (6 feet)

Mounts: Various, including Canon FL, M42, and Nikon1

Weight: Approximately 400 grams (14.1 oz)

Design and Build:

Manual Focus: The lens features a smooth manual focus ring, allowing for precise focusing.

Aperture Control: The aperture ring is manual, with half-stop clicks from f/3.5 to f/32.

Build Quality: Constructed with a metal body, the lens is robust and durable, typical of lenses from this era.

Special Feature: Built-in retractable lens hood1.

Optical Performance:

Sharpness: Known for its good sharpness, especially when stopped down.

Bokeh: The lens produces a pleasing bokeh, thanks to its 6-blade diaphragm.

Color Rendition: Delivers natural and accurate colors.

Contrast: Good contrast, even in challenging lighting conditions.

Usage:

Ideal For: Portrait, nature, and general telephoto photography where a longer focal length is beneficial.

Compatibility: While designed for various mounts, it can be adapted to modern digital cameras with the appropriate adapter.

This lens is a favorite among vintage lens enthusiasts for its combination of build quality, optical performance, 

and the unique character it brings to image