Say 85mm lens to a photographer and depending on that individual person you will get different answers. The reason is that for a long time, the 85mm was the de-facto portrait lens. It's still ideal for portraiture to be sure, but an 85mm can do so much more!
"Ok smart guy", you may be saying, "what other use is there for an 85mm, especially a really fast 85mm like the one you are writing about"? Aha I would say, because the 85mm is incredibly versatile, especially when it's a fast lens. So let's accept that it's great for half body portraits on a full frame and reasonable head shots in close on a crop sensor. Back it up a bit and you can use it for detail shots in real estate. It's also great for pet photography giving you enough distance not to be crowding the pet, but not so far away as to encourage the pet to come see you (dog) or flip you the bird and walk away looking annoyed (cat). At larger gatherings, the 85mm can be wonderful for candids and impromptu images and is a favourite of wedding reception photographers because its minor perspective compression is more forgiving to the face than the oft misrepresented 50mm. In my fictional primes only kit, there is always an 85mm because of its versatility. If you shoot street work and are open about it, the 85mm is a great choice for environmental work, especially if you don't want to be crowding your subject.
Choose an 85mm that is optically fast and you can benefit from razor thin depth of field for close in work so the eye is sharp but the tip of the nose and the front of the ear are starting to soften nicely. If you have out of focus highlights, a good quality fast 85mm can represent them nicely.
This lens, from Sigma, delivers on all of these. While Sigma has been slow to replace this proven performer with an ART variant, they haven't had to rush because this lens is so very good. Image quality is excellent, distortions are very well controlled and vignetting is minimal. In fact, turning Lightroom's Lens Profile Correction on and off shows you how good the native images are.
While you can certainly use the lens for pseudo macro work as in this example, it's actually a bit nicer from a bit back to focus viewer attention and to compress the perspective a bit. I find the 33.5 inch minimum focus distance to be ok, but I would like it to be closer.
When shooting outdoors, the wide maximum aperture allows you to really manage your depth of field if you shoot wide open so even a landscape style image can have very specific in and out of focus areas. In this HDR example, produced using Macphun's incredible Aurora HDR Pro, we create a sense of mystery and menace on a generic path in the woods and the shallow depth of field near the vanishing point gives the viewer's eye a specific place to go to.
The Sigma 85mm f/1.4 is a good prime to have with you, It's not overly large and still focuses quite quickly even given the very shallow depth of field it delivers. Sigma delivers a hood in the box as well as a hood extender when the lens is used on a crop sensor body. I confess that I like this attention to detail from the folks at Sigma. For those that use them, the lens accepts 77mm filters. The aperture is built from 9 separate blades, so it generates a near circular out of focus highlight, so popular with the bokeh hunters.
I've read other reviews of the lens and some earlier ones have been unhappy with the lens, specifying that it didn't focus sharply out of the box. I have only shot two instances of the lens, both in Canon mount and both were tack sharp, so my experience does not echo that of other reviewers who reviewed the lens when it was first released.
And that may be the only real caveat here. This is the old style Sigma build. It's not one of the ART, Contemporary or Sport designs and that means that at some point, Sigma will likely replace it. I think that they have more important fish to fry first such as their 70-200/2.8 but they don't ask my opinion on what to do next. I confess I prefer the barrel finish on the ART series but I own the pre-Sport version of the 120-300/2.8 and admit that the finish is a heck of a lot less important than the image quality.
Landscape images are usually not the first use case for an 85mm. I like it for the right composition because of the subtle apparent perspective compression and the incredible sharpness that the simple lens design delivers. Even with the definition of crappy light I had on the go outside and shoot ignore the weather day, the tonal range and rendition delivered by the lens is really nice. Sharpness is excellent
We'll close with a classic portrait shot. I shot this young lady with my general go to lens for portraits and headshots, a Canon 70-200/2.8L II and then with the 85mm. The 85mm version looks very nice and it could give shallower depth of field if I so chose.
As we come to the close of this conversation, let's take a look at the economics of a fast 85mm As usual, I will use the usual suspects, the options from Canon and Nikon. Canon doesn't do an 85/1.4, they offer only the 85/1.2 which due to the wider maximum aperture is slower to focus than the Sigma. Nikon has their widely acclaimed 85/1.4, a well proven performer. The Sigma is available for Canon, Nikon, Sony and Pentax mounts and is presently selling for $1579.99 CDN so a substantial investment. Nikon's lens is currently selling for $2099.99 so the Sigma saves you just over $500 if you choose this route. The Canon is not truly a fair price comparison but is presently on sale at $2699.99 with a ⅓ stop larger maximum aperture. Your use cases will determine the viability of which lens best suits your needs. From a quality perspective, it's pretty hard to beat this Sigma offering.