I will try my best to not make this too long, but given I'm longwinded, I will likely fail!
What I love about the 135/2 Apo Sonnar is that at it's best, it gets out of the way - it has a clarity that only comes with prop;er contrast (both global and certainly micro contrast) and proper correction in the color domain. It simply doesn't impart itself onto the scene much - thus it has high (subjective) transparency and honesty. So that means if you're shooting a scene with true, real high frequency detail (and to be clear, not every scene, in fact, likely many a scene, does not containis), everything is preserved. Subtle differences are rendered quite well, things look realistic. The old train window analogy I've used before we'll trot out again. Scenic train in the alps, scenery is gorgeous. In the cheap car, in the back, you look out at the scenery through a plexiglass window with some scratches. Scene is still beautiful, you're thinking "wow, a trip of the lifetime". Then a guy you meet at the bar, who has a berth in the first class section, invites you to the dining car. Instead of plexiglass, you have really good glass for windows - so the view is even clearer. You have more of a direct connection to it - "there is less in the way", so to speak. You go "wow, you know, the first car was good, but man, this is better - it's great". The conductor hears you talking, and he's in a good mood, so he invites you to the locomotive, and there the wide window has been opened, and you have a view of the scenery, with absolutely no glass window or anything - just clear air between your eyeballs and the scene. Even better - more connection, more clarity, "less in the way", more transparency. So there is a progression of improvement. The plexi window in the budget car is your kit lens, your 28-300 zoom, your older AF-D prime that isn't that well corrected. Still good - no doubt, but not exceptional. The glass window in the first class dining car is an upgrade in terms of transparency and clarity - more direct connection, more realism. This is your really good pro manufacturer F/2.8 zoom, your basic good fast primes - 24/1.8G Nikon, Sigma 35/1.4 Art,, Nikon 85/1.4G, so on, so forth. The last experience - no glass at all - that's much, much rarer. That's your reference quality glass, your 200/2 Nikon, your 135/2 Apo Sonnar, your 85/1.4 Milvus and Otus, any of the 300 and 400 exotics. Not cheap. But they all share this same "get out of the way" quality. But it's an exclusive, rare club.
Yea, I know, I said I would make this quick (oops!) and I haven't even talked about the Milvus 85 yet. What I found, shooting both lens on the west coast recently, is that while neither lens gets to this level of reference quality wide open or at the first apertures near it, is that once you stop the lenses down into the landscape apertures, THATS when the "wow", this transparency, this last "no window on the train" occurs, within the context of *maintaining this quality through the edges of the frame*. The big difference? I find that with the Apo Sonnar I have to be a stop to a stop and a half (give or take) further stopped down to "enter" this quality "zone", if you will, and with the 85/1.4 Milvus, I don't have to be. Obviously assuming you have sufficient DOF. And we're talking at distance. I think the apo sonnar might have a slight edge in sharpness in closer ranges (although both are superb).
What this allows you to do, of course, is (with the Milvus 85) shoot at an aperture that is a bit further away from the land of diffraction, because the edges maintain the excellence better and "earlier" on the aperture dial than the apo sonnar. The apo sonnar (and the 85 otus) might have a bit better, in the very slightest degree of magnitude, central zone and central zone only resolution and micro contrast, but neither lens (I've shot both) maintains this quality to the edges as well. So it's a minor design tradeoff. In terms of walking you through an example, if you're in the US or ever been to the Heceta Head lighthouse north of Florence, OR, there is of course the often photographed view from the highway. LIghthouse near center frame, and the rock and trees it sits on to your right. Lots of foilage, and some details on the rocks because birds nest there. Nothing to the left of the frame (ocean) in the traditional 85 or 135mm view here. With the Apo Sonnar, even though everything is at infinity here, I am happiest with the textural detail and realism of the tree line if I'm at F/9, not really any earlier. Same shot, same day ,the Milvus 85 will achieve the proper textural detail and realism of the tree line and you can get away with F/5.6, maybe F/6.3. In an extremely subtle sense, I think the Milvus actually delineates the very fine tonal and color differences in the tree line a little bit better than the apo sonnar, but it's an extremely slight difference - both are excellent, and both are much better at providing these subtle differences than your 70-200/2.8 pro zoom or even an otherwise excellent lens like the Tamron 85/1.8 or Nikon 85/1.4G. I think it's because the Milvus design just slightly sacrifices the ultimate in central zone (which is the 85 Otus) to maintain the edges just a bit better through the majority of the frame. So if the Otus is a 10 in the central zone, the Apo Sonnar a 9.9, the Milvus is a 9.8. But at the edges, generally saying, the Otus and Apo Sonnar are maybe a 9 while the Milvus is a 9.3. Since I value, in a landscape lens, edge to edge performance, that's why I'm absolutely head over heels in love with the 85/1.4 Milvus. I honestly would not take an Otus in trade for that reason. Others obviously would - it depends on what you value the most. I can say, at this point, owning the 200/2, 135/2 apo sonnar, and the 85 milvus, that for what I value in a landscape lens, the 85 milvus is my favorite out of that very, very good group of reference grade lenses by the slightest of margins. When faced upon a scene, I always try the Milvus first to see if 85mm makes sense for the scene. If it does, great, if not, obviously I move on to the proper focal length. But Zeiss did something really special with that lens that matches up to what I value in lens performance, which is really what it's all about - figuring out what you value and which lens or lenses work the best within that viewpoint.
Very Important Note: The deepest of the deep corners of the Milvus are not amazing. The edges hold up, insanely so, but the very deepest corners of the Milvus never come into the range of excellence that the rest of the frame has. Doesn't bother me for what I do, but you should be aware of this.
So, to clarify, these are two world class lenses, some of the very best you can get, but I do see these differences after some extended usage now, but be aware the magnitude of difference is slight. But when you start comparing reference grade glass, that's what you will see. Someone (I think) who is "central zone" biased will be better with the apo sonnar and 85 Otus. I prefer a touch more evenness, so the Milvus is about as perfect a landscape lens as I've used... the deep corners are not likely to be in the frame as I probably will have a very slight crop going on (and the Milvus is a "loose" 85 - as opposed to the Tamron 85 which is almost a 90 in some ways, feel wise)
Hope that helps. At this level of performance, you need to rent to see how you feel though.
-m
