The D FA28-105 has gotten generally solid praise here on the forums since its release in 2016 for the K-1. As a walk around zoom the 28-105 range has been a favorite for years as demonstrated by this being Pentax's 4th autofocus version of a 28-105 lens. In addition, Sigma made at least four models of 28-105 in the film FF autofocus days and Tamron another that is said to be the same lens as the
SMC Pentax-FA 28-105mm F4-5.6 [IF].
What I can't find anywhere is a comparison across 28-105s, both current and historic, with any attention to IQ. The Sigma's are generally poorly though of in the reviews (the UC III & DG versions being the exceptions) and the Tamron's rating in the review section is significantly higher (8.54) than the same lens when rebagged as a Pentax (7.21).
The reviews of the new D FA28-105 are generally glowing with a Forum overall rating of 9.13. It has the new HD coatings (the older three are all SMC) and the lens features nine rounded diaphragm blades for smooth Bokeh. It is weather resistant, and the front element is SP coated which helps repel water drops and grease. It also has a silent DC motor but unlike older silent Pentax lenses has no provision for back-up screw-drive. It has no aperture ring, being intended solely for use on dSLRs. 92% of the 25 reviewers would recommend it to other Pentaxians. On the other hand the FA28-105 Power Zoom lens is recommended by 100% of the 21 reviewers. And at an average cost of $85 (and I know that they can be acquired far more cheaply today) versus $500 for the DFA model, the cost difference between the two could be a factor for many.
Why is it that no one really looks at the older lenses in comparison to the newer ones? There are any number of threads and posts on the forum beating the "if its new it must be better" drum. One answer may lie in a very long line of social psychology research into the impact cost has on one's perception of quality. Basically, the more one pays for something the more strongly one will defend that item and the more highly one rates it in comparison to other goods available. Very straightforward studies where the same item was given two different prices, same item, same description, same sales materials, simply different prices resulted in massively higher ratings for the higher priced item ($199 vs $19 for the same radio for example). Could this be, at least in part, a cause for the 9.13 for the new DFA 28-105 despite negative comments within the reviews that are disregarded? Could the softness in the corners for the Power Zoom FA 28-105 be more noticeable because it costs less?
When I did a little side-by-side comparison on 3 Pentax zooms at 300mm it was funny how the highest rated one was not the one most frequently chosen as the most pleasing. Could it be that the rush to buy "modern" FF lenses is just that - a rush?
Last edited by Docrwm; 03-02-2019 at 09:16 PM.