Originally posted by audiobomber I disagree that the 40mm XS is as good as an smc DA 40mm Limited. I owned both at the same time. Chromatic aberration on the XS was disturbingly prominent and not addressed by standard CA suppression in LR. DXOMark agrees on this point, showing double the CA for the XS version. Also, shooting without a hood is not acceptable to me, veiling flare was obvious vs. the Limited with its tiny hood, even on images taken indoors. Sure, you can add a hood, but then the smaller size is lost. I believe the XS uses plastic elements for cost and weight savings, the Limited uses glass, as in the DA 35mm vs. FA 35mm.
I would definitely go for the HD 40mm Limited over the smc 40mm for the improved coatings and rounded blades. I would not trade my smc DA 15mm Limited for the HD version for the reason mentioned above, starbursts. Rounded blades will improve the bokeh, but there's no real bokeh with the 15mm. I've never shot with an HD 40mm but the smc 40mm could do with smoother bokeh.
perhaps you had a bad 40mm XS ?
I haven't had a problem with mine and I refer you to the in depth review of the Pentax DA 35mm F2.4 vs 40mm XS vs 40mm Limited
https://www.pentaxforums.com/reviews/da-35mm-40mm-limited-xs-shootout/introduction.html
are the two lenses interchangeable no, but neither is the price
" Summary
Though we really like all three of these lenses, . . . let's get down to dissecting how these three stack up. As we've indicated above, we feel that the
DA 40mm f/2.8 Limited is the most complete package among those presented here. While our review copy had some issues, we are certain that they are not representative of the model's true performance, which should very closely match what we've seen from the DA 40mm f/2.8 XS in these tests. The 40 Limited has the best build, the best looks, and the best features—
but for a relatively steep price.
The DA 35mm f/2.4 and the DA 40mm f/2.8 XS also have much to recommend them. . . .
The DA 40 XS is by far the smallest and lightest APS-C lens currently being made, and is a brilliant street-shooting tool, much like its skinny-but-not-emaciated elder brother. We find 40mm to be a bit of a swiss army knife focal length on a crop-sensor camera—take a few steps toward your subject and it becomes a lovely short portrait lens, take a few steps back and it can capture landscapes, architecture (to a certain extent), and serve as a general walk around tool.
Ultimately, any of these three will get you great image quality, durable construction (if a bit chintzy, in the case of the DA 35mm), and a compact and lightweight package. Honestly, despite our desire for a faster or slightly wider normal prime, Pentaxians today are a bit spoiled for choice in this general ballpark, and all of the choices are good ones. . . . "
Pentax DA 35mm F2.4 vs 40mm XS vs 40mm Limited Review - The Bottom Line | PentaxForums.com Reviews