After the first look review on the Sony FE 70-200mm f/4, let's continue with a more specific assessment on its use and results.
This lens category is a favorite with a wide variety of photographers. First off, they are the darling of photojournalists everywhere, enabling them to capture action (reasonably) up-close while giving good reach in case one needs to stay safely away from trouble. Sports shooters also use them quite a bit for indoor activities, and they nicely suited to events such as concerts. Even the f/2.8 variants on a 35mm sensor can't provide ultra shallow DoF for portraits, so they will not be the first choice for portrait shooters. Still, especially in the studio, they are a popular choice, given the focal range provides a complete coverage of "portrait" focal lengths.
In the few days I had my hands on the lens, I took it with me on two events: a live music/dance event and a fitness/bodybuilding competition.
First off, let me reiterate my approval in the handling department. It is what a discerning user would expect from a pro lens, meaning, it gets the job done without having to think about it that much (and this is high praise). Operation is silent, of course, the lens focuses internally, and doesn't extend at all.
Sony even equipped the lens with three focus lock buttons, for use in fast action situations. From the little testing I did on action shooting, even the older a7, which would hardly be called an action camera, responded very well, while on good light. The lens is definitely mechanically capable of action shooting, and the limitations are with the current a7 line of cameras for this purpose.
In low light, on the a7, the focus can hunt a little, and, most of the time, will find correct focus if you immediately refocus (back focus button and setting the focus limiter on the lens to the correct distance range also helps a lot).
Almost all photos in this post were shot wide open, and the one impressive thing was that the lens is very sharp even at widest aperture. It's absolutely great in the center and very good at the edges, while everything gets sharp at between f/5.6 and f/7.1. Please check out the gallery in the previous entry, to see samples at various apertures. This holds true of about all focal lengths: common to lenses of this sort, it is stronger at medium lengths and suffers somewhat at 200mm.
Again, let's not forget about the impressive sensor in the a7. As I said, this is an earlier incarnation of the core sensor, which is still used (upgraded of course) in cameras announced -literally- yesterday (the new Leica Q). It retains color and dynamic range easily to ISO6400 and, although there is grain visible, it is easily sorted out in post processing. The lens contributes with very good contrast and color reproduction, reminiscent in fact in some ways of older Minolta lenses. What I'm trying to say is, you can't put good glass in front of crappy electronics or vice-versa. This lens compliments Sony sensors in a honest way.
Distortions and light fall-off, across the focal range, are pretty minimal: also remember that the camera enforces corrections even in RAW, and RAW-converters take care of the rest. The lens profile in LR works perfectly, corrections being precise and effective. I also noticed no CA and I suspect these are also being taken care in camera. Flares were also non-existent (although I'll admit I didn't try to force it to flare, but did shoot into the light quite often).
A crucial characteristic with a lot of users, but especially portrait shooters, is bokeh, and here is where the lens, surprisingly, performs above the average of its class, and is, in fact very useable from f/4 to about f/6.3, if smooth out of focus rendering is what you're looking for. It has no chance matching the creamy, dream like bokeh of dedicated portrait lenses, but, again, being 2-3 stops slower, this is no surprise; no zoom in this class really can. Risking being repetitive: these lenses are general purpose ones, and should be judged as such.
Finally, it's time to consider the obvious question: is the FE 70-200mm a good value?
Personally, if I'd started investing in the FE system, this would be the second lens I'd buy, after the Zeiss 55mm f/1.8. Why? Because it's a choice that exceeds its characterization as a "practical" choice. On paper, one could raise several "complaints" with this lens. Why isn't it a f/2.8? Why isn't it a couple hundred euro cheaper? Why don't they give it out for free with every a7, come to think of it?
In practice, it is what it is, and it does its job almost better than one would expect. Initial price was rather high, but since then has dropped to practically the same levels as competitor DSLR lenses in the category. Alternative options for the FE system, speaking of AF zooms, are not that hot either. One can adapt a number of lenses for the Alpha mount, such as the venerable Minolta 80-200mm f/2.8, the Sony 70-200mm f/2.8 or, for a much cheaper choice, even the "Beercan" 70-210 f/4. All these need a rather expensive adapter to autofocus, and are heavy, noisy, slow to focus, or all of the previous combined. I also doubt they have critically better overall IQ, especially at f/4-f/5.6 (I'm not talking only sharpness but also color, aberrations, distortions, etc).
As I said in another instance: if one trusts Sony in their FF line of mirrorless cameras, better performance bodies will certainly come; just look at the just announced a7R mk2. Being forced to use a crippled lens is catastrophic; camera bodies are easily upgradable. Fortunately this lens can keep up, I believe, with the improvements in sensors and camera AF systems, so, objectively it represents a solid addition to the FE arsenal.