True, but whether the WR version has aperture ring or not has nothing to do with its DFA designation. What makes a lens a DFA?
A New Series Designed to Optimize Image Quality in Digital SLR Photography
PENTAX Corporation is pleased to announce the development of the new
smc PENTAX-D FA interchangeable lens series, designed to optimize image
quality in digital SLR photography. The series also features an image circle
covering accommodating the 35mm-format film. As the first models of this new
series, PENTAX will market two compact, lightweight macro lenses for close-up
photography up to a life-size magnification.
Major Features
1. High-Performance Optical Design to Optimize Digital Imaging Characteristics
Taking advantage of its advanced optical design technologies, PENTAX successfully optimized the optical characteristics of these new lenses for digital photography, including lens coating and curvature and positioning of optical elements. In particular, flare and ghost images - the most disturbing factors in digital SLR photography - have been reduced to minimum for clear, high-quality digital images.
2. Image Circle Compatible with 35mm-Format SLR Cameras
The new lenses features an image circle accommodating the image size (36mm by 24mm) of 35mm-format SLR film cameras. As a result, they produces high-quality images with edge-to-edge sharpness and free of vignetting, even when mounted on conventional 35mm-format SLR cameras.