I'm starting writing up this test without having tried it. At this stage, I have no idea what the results will be. But let me start with the idea behind the test.
I've owned the Canon 17mm TS-e for a few years. I switched to Sony mirrorless a while back. My solution for Sony due to the lack of good native E mount lenses has been to mostly use Canon lenses with either the Sigma MC-11 or Metabones adapter. There have been some down sides to this solution but on the whole I've been pretty happy.
So I was at the pawn shop a couple of months ago - and stumbled upon a few items. One of which was a Metabones Speed Booster! Frankly I've got so many new toys I've had little time to test this out. But I had an epiphany- what would happen if I put the 17mm TS-e on a full frame camera? Honestly I don't know yet as I write. The image circle of the lens is huge! On full frame with no adapter, there's 12mm rise-fall.
So my theory is that the lens-adapter combo will result in a 12mm f2.8 lens that might cover full frame!
------------------- ok, the results are in ---------------------------
So, just having tested my theory, it did NOT work. The image circle with the Speedbooster is far too small and vignettes massively. The 17mm TS-e on the A6000 seems to work fairly well. However, there is a little distortion, and when shifting vignetting appears well before the 12mm shift, in vertical position I noticed it around 9mm. What else is weird is that the vignetting appears in the opposite position: when shifting upwards for architecture, the vignetting cropped up at the bottom! I'm still trying to wrap my head around this.
On the plus side, despite the extra glass, the results are super-sharp. You can see and download full-resolution samples here (for your own personal use of course.)
|17mm TS-e with Metabones Speed Booster on Sony a6000
|17mm TS-e on full frame Sony A7rII