Ultra-wide angle lenses have long had a tendency to be expensive. Especially the fast constant-aperture zoom lenses. For my 35mm film use many years ago, I purchased a Tokina 20-35mm f/3.5-4.5 having a 77mm filter size and metal construction I found to be quite sharp and delivered fine results. The Tokina 19-35mm f/3.5-4.5 already mentioned also enjoyed good test reviews, and its plastic construction is pretty good.
---------- Post added 04-20-20 at 03:58 PM ----------
Originally posted by normhead I have the Rokinon 14 2.8, a very good lens if you get a good copy. I have my FAJ 18-35. My DA 10-17 covers the FF circle at 17mm and 16mm, My Sigma 8-16 covers the FF circle at 16, and 15mm.
I honestly don't spend a lot of time fretting about lack of lenses for UWA. I did for a while because in theory the situation sounds terrible. I bought the Rokinon 14 and discovered I just don't have a lot of call to use it. For just walking around my FAJ 18-35 is light weight and very portable and just the kind of lens you want when you know it won't be used often but you want something for just in case. And it cost me $100, new in box old stock.
FAJ 18-35 at 18mm, you could do a lot worse.
That FA-J lens is FF from the 35mm film days and the image quality looks good to me- and not adding a lot of weight.
---------- Post added 04-20-20 at 04:03 PM ----------
Originally posted by house The OP is asking specifically about FF lenses.
Wide angle apsc lenses usually perform even worse than telephoto ones and with wide angles you are less likely to be going for subject isolation. Two aspects that make using apsc wides on ff a bad idea. I've tried to use the da 12-24mm but the the limitations coming at you from all directions make it not worth the hassle. Vignetting varies dramatically by aperture and of course zoom, edges are never good etc. Keeping all those limitations in mind when shooting becomes very cumbersome and prone to mistakes.
I would expect vignetting with this lens on FF, maybe affecting the edge performance. On APS-C, testing established uncommonly good edge performance, and fine results through the aperture range.
The DFA 15-30mm f/2.8 is an outstanding ultra-wide zoom lens, but it is a heavy beast, and very expensive. I don't see why Pentax could not again make a variable-aperture UW FF zoom lens as it did with that FA-J model, and with WR to boot, at a reasonable price.
If I get a FF DSLR body, I will simply put my Tokina UW zoom back in service for digital use, and that will be good enough. As it is, I am very satisfied with my high-performing Sigma 10-20mm f/3.5 on APS-C for my UW needs.