Thats is not an easy question.
Each of the lenses have something in their own signature.
My most used i serie lens is the 45i. I used it next to the 35i for about a year. The 35i is the best package if 35mm focal lenght and compact size have your preference. My copy was very sharp from f2.5 into the corners. Biggest plus is its bokeh.
65i; Sharp tool in the shed. A big difference in rendering compaired with the 45i or 35i
F/3.5 24i great package stopped down for landscape and city. Misses punch wide open.
90i using the lens only one month now, but very impressed by its IQ. Very small without the hood.
I had the Sigma 50mm F2 DG DN, or 50i, for a couple of days. Unfortunately I had a few moments here and there only to try it out. My findings, and opinions:
Sharpness (as in contrast and resolution when used together with the 24MP A7C): The center and about a third of the image out towards the edges is good. Resolution goes down somewhat sooner than i expected from the Sigma advertising material. Corners are weak.
LoCA: Pretty good, there is some but not much to complain about. The same for LaCA.
Bokeh: Pretty good, I had no objections really. Some might dislike the onion rings when printing big but for other uses it was fine. No double lines or very harsh backgrounds. I don't think anyone would call the bokeh busy. One thing is that the mechanical vignetting, I guess, make corners less blurry than wished for in some situations.
AF: Works fine in CAF mode. There are situations when camera and lens combination hunts a little but that is user error I think (not much of vertical lines for the system to use for focusing). In DMF mode it's a bit slower.
Aperture mechanism: In CAF and MF mode OK. In DMF mode the aperture blades closes and opens back and forth upp when focusing. Not in a snappy Sony way but step by step. Annoying.
Aperture blades. Small sunstars possible if you stop down a lot. So not really. I like that but if looking for sunstars this isn't the ideal lens.
Flare: Not that good. It simply flares easy if the sun hits the front element. The result is color shifting and low contrast.
Build quality: Great. A question mark for the weather sealing.
Focusing ring. Focusing by wire of course and, of course again, no scale. That's bad. OTOH is the ring better dampened than the Sony focusing rings and it works well.
Aperture ring: Always clicking. Unfortunately it can be slippery when shooting vertical (I usually turn the camera counter clockwise when shooiting a vertical image). I don't know why they design aperture rings this way with nothing to grip where the aperture scale is.
Features: I never tried the original hood as it is too bulky to my taste. A standard screw on metal hood looks better and works as well. I also never used the gimmicky magnetic lens cap (as i like hoods).
The MF-AF control slides vertically rather than the horizontal Sony way. I like the Sigma approach and the white background inidicator is nice as well.
Unfortunately there is no control button on the lens.
Some images, or many, sorry for that but they should load quickly:
LoCA:
Bokeh up and close, the whole image and then a crop:
More bokeh, at f/2, f/2.8 and f/4:
More bokeh and cat's eye, f/2, f/2.8 and f/4:
At a distance, you can use the lens wide open (or I did) most of the time:
Background rendering, shooting distance somewhere around 1.5 meters:
Flare, this was stopped down but it wasn't that much better at f/2:
Just a quick FYI in case people haven't seen, but Sigma in the UK (not sure elsewhere) currently have a rather good cashback offer (£70 off most of the i series).
Hopefully this is useful for others like me who lurk this thread and have been planning to buy. I just pulled the trigger on the 24/3.5 to complement my 35/2.
I have added it recently and comparing to my other 50s. I have quite a collection. 50/2 Loxia, 50/1.2 GM, 50/1.4 GM, 55/1.8 ZA, 50/2.5 G, and even 40/2 CF Baiis. Haven’t come to a decision yet because but hopefully will soon. By the way those are just the 50s I have in FE mount. Have older ones from the film days in K, F, M, and EF mounts.
