I'm not a pro, I'm a hobbyist. But you hardly need to know what you're doing to get good results - it's almost cheating.
For a while now, Sony has received criticism for not providing enough professional lenses to work with. For the E-Mount system, serious photographers have no choice but to pick up the Zeiss lenses such as the Distagon, Plannar, Loxia and the Batis lenses. However, many pros are still loyal to Nikon and Canon's faster primes and zooms. As of the writing of this review, there are now 4 GM lenses to choose from. And I think these may be the lenses that will finally lure professional DSLR loyalists.
The 85 f/1.4 GM is beautifully crafted. It's huge and very long with the hood attached. It is also heavy, but feels very balanced on my A7R II. The construction is solid with no room for compromise. Overall, the body is mostly made of metal. The focus ring is rubber coated for easier grip but the aperture ring (YES, AN APERTURE RING!) is metal. The lens cover and hood are both plastics. While the lens cover is standard for all lenses (at least as far as I can tell), the hood is much more solid. The edge of the hood is rubberized and the inside is coated with a cloth-like texture which I think helps capture dust before they get on the surface of the lens. The hood also have a little button or clip to the lens, which I think is a nice touch. To top it all off, this lens is weather sealed.
The lens comes with 2 switches: one to switch between Automatic Focus or Manual Focusing, and the other is to turn off the clicking noise it makes when changing aperture through the aperture ring. I reckon this is very useful for videographers out there who want to eliminate as much internal sound as possible. It also has a custom button the left side of the lens, I assigned it to be my primary Eye AF when using this lens and together with Continuous AF, continuous Eye AF will change your portrait photography because it will allow you to have perfect focus almost all the time at f/1.4!
The lens (pros):
At the asking price of a whooping $1800, it better be good! And it's very, very, good. With my A7R II, the photos I take are sharp, the bokeh renders to beautifully, the colors are dreamy, and it's very addicting. The functions such as the additional Custom button makes shooting with this lens very easy to get used to quickly. It is quite possibly the best portrait lens in the market today.
The lens (cons):
The most obvious one is the price. The AF rotors are noisy, like rocks grinding together. It also doesn't have Optical Steady Shot (OSS) for the older A7 bodies or APS-C bodies like the A6100 or A6300 to take advantage of.
As of today, there are three 85mm native Sony e-mount lenses to choose from. Sony's FE 85mm f/1.8 ($600), Zeiss Batis 85mm f1.8 ($1200), and the Sony 85 F1.4 GM. The price difference between the three is not easy to ignore. As a hobbyist, I was set on getting the Batis 85 until I found an open box of the 85 GM offered at Best Buy. If you have the money, go for it. It's been one of the best purchase I've made in a very long time. Besides, lenses will serve you for a very long time if you take care of them!