Originally posted by StigVidar How many of you in this 'club' has gone from DA*55/1.4 to D FA*50/1.4? What is the main difference between those two? I have myself the DA*55/1.4 and are not really using it at f/1.4, but find it good at f/1.7 and excellent at f/2. Green and red CA is troublesome in high contrast images.
Perhaps the most annoying with DA*55/1.4 is focus inaccuracy, but that has changed to the better with K-3 III. How is that on D FA*50/1.4?
I fall into this category, although I have only owned the DFA *50 for a few weeks and had the DA *55 for 8 or 9 years (maybe longer -- I can't really remember). These are the differences I see.
1. The DFA * 50 is a true full frame lens. I got some shading when using the DA *55 with the hood on a K-1 and there was quite a bit of vignetting even at f2. The DFA *50 is a lot better in these respects. You don't have to take the hood off the DFA *50.
2. The DFA *50 focuses better. I don't own the K-3 III, but my experience with the DA *55 did have a little flakiness with regard to focus. More than that, the SDM on the DA *55 is just really slow -- the slowest of any SDM lens I have used. The DFA *50 is no speed demon, but it is able to snag focus on moving objects, which the DA *55 seldom could.
3. Fringing is less with the DFA *50. It isn't really bad with either lens, but certainly less with the 50mm lens.
4. Wide open performance isn't close. The DA *55 isn't really usable wider than f1.8, in my opinion, even on APS-C and the DFA *50 is excellent even at f1.4.
I think the contrast is good on both -- not much difference. Stopped down performance is similar. Flare resistance is a little better with the DFA *50 -- maybe partly because you can actually use a hood with it.
Others can probably give more information.