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Not intended as a recommendation for any particular lens, I thought I'd share my thought process on deciding what wide angle lenses I wanted for my D800.
I too wanted a wide angle lens for a "general" photography use case, which for me means everything from some limited street photography to environmental portraits to landscape to documenting day to day life. Up close and far away, day and night.
Such a use case for me makes me think of a 35mm, or a zoom encompassing the range of at least 28 and 35mm. While I love (or used to love) 28mm for mountain sport photography (used to be my thing) I find 35mm a better fit for me for an all-round normal lens. I've not adapted to zoom lenses but if I were, a moderate to wide zoom might be just the ticket.
You have manual focus 50 and 100mm Zeiss primes; I'm coming from an all manual focus Zeiss lens history myself but have rather deliberately looked for auto focus options in choosing lenses this time around. Having at least one AF lens at your disposal might make sense, especially a lens for "general" photographic purposes and where kids or other fidgety subjects are involved. A ZF35/2 or /1.4 tempted me, but AF won.
Will you find a 35mm a big enough departure from your Zeiss 50 to justify a purchase? Only you can tell.
For me the answer is yes and because I don't much like 50mm, I have a cheap, almost disposable, Nikkor 50. For whatever reason 50mm and I don't get on very well; sure I can use it but I'm mostly always wishing it was a little wider and only occasionally wishing it were a little longer, whereas 35mm mostly feels just right to me and is in fact my "normal" lens. As such having at least a f/2 35mm was important to me for speed and depth of field for image making purposes, so a f/4 VR zoom or even a f/2.8 zoom didn't really appeal to me.
I ended up getting the Sigma 35/1.4 for the price/performance value proposition it offers. Unlike some very fast lenses, the Sigma is very usable at wide open and not just in the central region of the frame as it offers great sharpness over a decently large region of the frame even when shot wide open. Its manual focus feel is excellent - a little stiffer than a Zeiss MF lens but very good just the same. My Sigma 35 copy has very good and consistent AF performance using the centre focus spot; at the outer focus points, not so good. Someone here on FM was told Sigma has a lens tweak available for D800 users to address this so am waiting to see what their result is before considering sending mine in. In the meantime I use it via focus and recompose where necessary and occasionally manually focus the lens.
Before buying a lens or lenses I try to think about what will come next, because if I don't, I end up with a bunch of lenses, some of which don't get used much.
My dilemma is what to buy for a wider than 35mm view. I'd like to have a focal length available to me somewhere in the range of 20 - 25mm, but unlike the 35mm, this lens won't be used all the time. The ZF21 appeals to me greatly, but for a less used lens I'm not sure I can justify the cost or the weight of carrying it around.
For heads-down serious landscape panoramas I'm more inclined to do multi-shot stitching with the Sigma 35 rather than add a really capable wide/ultra-wide; so what I really need in a wider lens is good enough performance for reportage style photography, deliberately exaggerated perspective at times, and the odd landscape snapshot for convenience. As it won't be used all the time, a less expensive lens will fit the bill, and a smaller lighter lens is a tangible benefit and mean it'd be more likely to be found in my small go-everywhere bag. AF is less of an issue for me at the very wide end of the scale, so I'm open to MF here too.
The foregoing is telling me I probably should look at the Nikkor 20 AF-D, or perhaps a Sigma or other third party brand lens, and maybe I'll keep the ZF21 and Nikkor 24/1.4 in mind too but both are overkill for my purposes for this particular lens. I'm hoping Sigma comes out with a fastish 21 or 24 or 25mm lens along the same lines of the Sigma 35 DG HSM. Another alternative would be to go with the 16-35 or 17-35 Nikkor zooms, even though they overlap with my Siggy, simply because they'd be so versatile. The Nikkor 12-24 would also be great but is just too big and heavy for my purpose.
My inclination is to go smaller and cheaper and pick up an older prime like the Nikkor 20/2.8 AF-D.