Originally posted by ehrwien I think I've read (must have been here) before that the 70 is supposed to be an adequate replacement for the 77. I've yet to try the 70 on the K-1 myself, but I think the 70 is more clinical and the 77 has more personality?
I have both. In this case, it is more like two different lenses, because of a more substantial difference in FL between the two. To make that even more emphatic, I seem to recall a lab test, revealing the DA 70mm came up a little shorter than 70mm. Lab tests of the 3 Amigos revealed absolute accuracy of each FL, hence the odd FL these lenses were given in their names. Once again, there is a stop difference in available aperture between these two.
The FA 77m is able to provide a very good result even wide open, although the edge performance lags until the mid apertures, where all results are superb. Bokeh is outstanding. But there is more tendency with digital for purple fringing under some circumstances.
The DA 70mm can deliver outstanding results, edge-to-edge, even wide open. Chance of purple fringing is very low. Bokeh is excellent, especially with the rounded blades of the HD version, which I have. However, it cannot quite bring a similar result as can the FA 77mm at f/1.8 aperture. The added FL of the FA 77mm helps also.
These are both super fine lenses. I am glad I have them both. Generally, I use the DA HD 70mm when I need its performance for edge-to-edge excellence and for scenes where I want a shorter FL for getting more in the frame. I use the FA 77mm when I want more reach for framing to better isolate subjects, and for low light conditions, and for closeups with extra-fine isolating bokeh. It is also great on APS-C for getting candid shots, with its amazingly small size for a fast lens of such substantial FL, allowing it to be less attention-getting.