Auto Tamron 135mm f/2.8

Manufacturer: Tamron
Model: JSG-28Au ?
Focal length: 135mm
Aperture range: f/2.8-22
Filter size: 58mm
Weight: 388g
Length at ∞ (M42 mount): 96mm (116mm with hood extended)
Lens hood: built-in
Minimal focus distance: 1.5m (5ft)
Serial tested lens: 664189

The lens tested is an Auto Tamron 135mm f/2.8 with M42 screw mount. The lens was mounted on a Pentax K100D digital camera with the Pentax mount Adapter K (#30120) and photographs were shot in RAW mode. There has been no digital post-processing other than resizing and saving as 8-bit jpeg. Test shots were made on a cloudy day. All photographs taken hand-held with camera built-in shake reduction enabled.

The lens is an all-metal construction, typical for most lenses of its time, and it certainly is not a light-weight in its category. It features a built-in hood and I estimate the filter size to be 58mm (I have no other lens with this exact filter size to compare). Apperture markings are f/2.8, 4, 5.6, 8, 11, 16 and 22, but half-stop settings can be used. The lens focusses from 1.5m to infinity and has an extra mark for infrared focussing (orange R). It possibly is the same lens as described here on the Adaptall-website.

The diaphragm has six blades and is located behind the rear optical element (see picture below). It's not easy to clean the rear glass.

Tamron 135mm f/2.8