The Pentax SMC DA 16-50mm f/2.8 ED AL (IF) SDM* lens is a premium wide-angle to medium-telephoto zoom lens designed for Pentax digital SLR cameras. Here are the key features and specifications:

Overview

Focal Length: 16mm to 50mm (equivalent to 24.5mm to 76.5mm in 35mm format)

Maximum Aperture: Constant f/2.8 throughout the zoom range

Minimum Aperture: f/22

Lens Construction: 15 elements in 12 groups, including two extra-low dispersion (ED) elements and three aspherical elements to minimize chromatic and spherical aberrations.

Filter Size: 77mm

Weight: Approximately 600g (21.2 oz.) with hood

Key Features

Weather and Dust Resistance: The lens is built with a tightly sealed construction, making it suitable for use in adverse weather conditions, enhancing durability when paired with weather-resistant Pentax DSLR bodies15.

Autofocus System: Incorporates a Supersonic Dynamic Motor (SDM) for smooth and quiet autofocus operation, along with a Quick-Shift Focus System that allows instant manual focus override24.

Optical Coatings: Features Pentax's Super Protect (SP) coating on the front element, which repels dust, water, and grease, making maintenance easier45.

Performance

Image Quality: Known for very good sharpness when stopped down, particularly between f/5.6 and f/8. However, edge performance at maximum aperture can be less impressive12.

Focusing: The lens has a relatively fast autofocus system but may exhibit some back-focus issues in certain conditions, which can be mitigated through adjustments24.

Applications

This versatile lens is suitable for a wide range of photography styles including landscapes, portraits, and general everyday use. Its constant aperture and robust build quality make it an excellent choice for both amateur and professional photographers looking for reliability and performance in various shooting environments35.

In summary, the Pentax SMC DA* 16-50mm f/2.8 ED AL (IF) SDM lens combines high-quality optics with practical features tailored for demanding photographic situations.