Originally posted by creampuff I have the DA*55, DA70 and FA77. The DA70 is cheap and good but just doesn't throw the background out of focus enough and the minimum focusing distance could have been closer. Wide open, it is sharp but there is also noticeable light falloff. If you have the budget, go with the FA77, it is a lot better imo.
Don't know if I would call the DA 70 cheap as I doubt you will find a new one for under $500.00. Both the FA 77 and DA70 are excellet lenses. The FA77 has the better bokeh but doesn't focus as fast and apparently has issues with PF in some circumstances. If you plan to shoot mainly portraits and really want the buttery bokeh than the FA77 is your lens. It will be up to you to decide if this feature is worth the extra $200 or more it will cost you for a new lens.
Klaus Schrioff of Photozone wrote the following regarding these two lenses:
"The Pentax SMC DA 70mm f/2.4 Limited is an great lens with no really significant technical weakness. The resolution characteristic is generally excellent regardless of the (tested) aperture setting and the resolution distribution is much more harmonic compared to the SMC FA 77mm f/1.8 Limited although it sacrifices a tiny bit of peak performance. There's a bit of vignetting at f/2.4 but it's not extreme and negligible when stopping down a little. Neither distortions nor CAs are field-relevant. You may be able to spot some traces of purple fringing. An interesting aspect of a large aperture tele lens is quality of the bokeh (the out-of-focus blur). Similar to its alcoholic counterpart it is a matter of taste to some degree - I'd say it is very good but not excellent. Here and there some of the out-of-focus halos seem to be a bit hard edged. The degree of background/foreground blur is also a bit limited by the comparatively small max. aperture (for a moderate tele lens). Typical for all Pentax Limited lenses the build quality is excellent and it is a joy to use such a high quality lens in the field. The price (around 500€/US$) is quite fair in relation to what you get here. Now is it a "better" lens than the FA 77mm f/1.8 Limited ? I'd be hard pressed to provided a real guidance here. Technically the DA 70mm is a bit better (more even resolution, less purple fringing) whereas the FA 77mm has a slight edge regarding the bokeh due to its larger max. aperture. Fortunately the choice is yours and not mine ... :-) "
Based on this review I bought the DA70 and I've been quite happy with it.
Tom G