So, you've decided to go retro with a Nikon D700 but you don't like my suggested 2nd lens choice. Well, maybe this one is more your style.

shot with a Sigma 60mm f2.8 DN at f7.1 on a GH5 body. 

Nice set up for products. 

I'm not much of a wide angle lens fan but two recently purchased lenses have gotten me further and further into the tar pit of shorter focal length image-making. Both are zooms and neither would be my primary recommendations for a third, bargain lens appropriate to match up with a "minty" used, decade old, Nikon D700. But both encompass a range that covers approximately 16-28 (or more) and when I use them I find myself gravitating more toward the longer end of their range. When I check the lens information I find that my super wide angle zoom lens usage falls into an equivalent of 28mm at least half the time. (One of the zooms is the Tokina 16-28mm f2.8, which has its flaws but can be a sharp, fun lens when used with care. The other is a much better behaved lens; it's the Panasonic-Leica 8-18mm f2.8-4.0 zoom. It's quickly becoming a favorite for establishing shots for videos when using the GH5!).

But I guess my point is that when I do use wide angles, unless I am constrained by my ability to back up, I end up in the 24-28mm range much more often than not. With that in mind, and wanting a compact and fairly light single focal length lens for those times when two pounds of zoom seem like overkill, I starting researching and testing the various 28 and 35mm lenses in the Nikon mount. Remembering back to the film days my first thought went to the 28mm f1.4 D lens (ultimately fast and sharp) but a quick check revealed that the current used price for that lens (with a glass aspheric element) is currently hovering around $2100. That one immediately fell off the list.

I narrowed my choices down quickly. I owned both of the 28mm f2.8 AF lenses and they were both ho-hum performers. Nikon figured out how to make their AF lenses a bit rattier and probably much cheaper; at least in this focal length and speed. The manual lens pictured here is the 7 element Ai version. The two AF-D lenses were: five elements in the first iteration (which was widely disparaged) and six elements in the second version (which was a bit better). The manual focus lens in this range that is widely believed to be one of the best is the Ais version of the above, (manual focus) lens which trades the 7 element construction for an 8 element design. It's the best of the 2.8 bunch.  I couldn't find one in good shape for a good price and so I compromised and went with the original Ai, 7 element version. Wide open the newer lens is supposed to be marginally better, in terms of overall sharpness and contrast, but by the time you hit f4.0 the differences shrink down to the point where only the most compulsively ardent lens analysts think they can see a difference. And then it's mostly at 300% magnification.

The model I bought (7 element Ai)  is in great shape and features a silky smooth, long throw focusing ring which makes it a great candidate for video as well as regular photography. I paid a whopping $125 for my copy and have used it often for location/industrial work. It doesn't flare, is scary sharp by f5.6 and better than just "usable" when used wide open.

The 28mm focal length makes a nice half of a two lens kit when paired with an 85mm. If I were specifically looking for a second lens to pair with the 105mm f2.5 Nikon lens I guess I'd be looking more for a 35mm focal length (so the gap between lenses isn't overwhelming) but so many of the zooms I already own cover that focal length nicely so I'm sticking with the 28mm.

Small, light, sharp, wide enough and dirt cheap. That makes it choice number three in my budget, full frame, retro kit. You could do a hell of a lot worse.

Find a used one at Amazon (or elsewhere).