Playing With Lenses: Pregnant Lens: SMC Pentax AF Zoom 1:2.8 35-70mm

Saturday, 17 June 2017

Pregnant Lens: SMC Pentax AF Zoom 1:2.8 35-70mm

Cost: $35 (average market price $115.80)

Collectors item alert!! This lens is regarded as the first auto focus lens on the market. For sure the first Pentax auto focus lens. The autofocus motor is build inside the lens, including space for AAA type batteries, giving this lens the appearance of a "pregnant" lens, ready to pop out a few small baby lenses... The autofocus only works on Pentax ME-F camera, but can still be used manually (push/pull type) on any Pentax PK compatible camera.

Due to the complexity of the build-in auto focus, Pentax had to make sure that the lens had constant aperture across the full zoom range, resulting in the fastest 35=70mm zoom that Pentax ever designed. The motor also increased the weight, making this a bulky heavy lens. And the design also left a minimal manual focus ring with only a quarter turn across the whole range, making this lens a little less friendly to use, and slightly harder to focus.

The lens also features a unique red coating that I have never seen on any other Pentax lens. But the colors are nice and saturated, requiring minimum post editing, and the lens has reasonable to good sharpness across the whole aperture and zoom range.

Pentax never made any other SMC Pentax-AF lens. Although a decent lens with a solid metal build quality, due to the unfriendly handling, it is mostly a collectors item, taking a well deserved place in Pentax history. A keeper for sure, but mostly to put on the shelf.

Lens Specification:

Focal Length: 35-70mm
Maximum Aperture: F2.8
Minimum Aperture: F22
Image Format: 35mm
Lens Mount: PK
Optics:7 elements in 7 groups
Blades: 8
Focussing: Manual, Auto Focus on Pentax ME F only
Minimum Focus: 120cm (unknown in macro mode)
Maximum Magnification: ?
Filter Size: 58mm
Weight: 580g
Length: 77-110mm
Production: 1981 to 1988
Serial Number: 8082341

Made in: Japan by Asahi Opt.Co.

More information on Pentax

Samples:
Pictures made with Lens Turbo II adapter