Sensor: Cons
Being the same sensor as the Ursa and the BMPC (a V2, but still), I knew the base ISO was 400. For us, that is really difficult to work with. I was very curious to try 60fps, and shooting at 60fps you lose an additional stop of light. On Friday, during the first wedding, it was really, really sunny. Not a cloud to be seen. Hard conditions for the sensor. The BMCC (and every other camera) struggles in these bright conditions, let alone the Ursa Mini, which has one less stop of dynamic range. I feel like its really important to expose to the right. The blacks get easily crushed and (when not shooting RAW), they are impossible to retrieve. ETTR is hard when your base ISO is 400.
I had some problems with this. During the ceremony the first day, there were windows behind the couple. The sensor couldnt cope with it, so I switched to my BMCC. In the morning, when the groom was getting ready, the room was quite dark. I managed with the light, but only at an aperture of 2.0. Again, not ideal. This wouldnt have been the case with a base ISO of 800.
No, this isnt a low light camera. I did try to shoot 60fps at the party on both weddings. With a lot of stage light and a LED panel as fill, it worked. But only just. I hate being intrusive at a wedding, and when blasting a big LED panel at the dance floor, you are being very intrusive. But the footage came out okay. No noise, but also not much detail in the blacks either. I tried ISO 800 for some shots (both at the party and during the day). It seems like there is still a little bit of fixed pattern noise -- a know issue with the 4K sensor. The shot that stands out most is a shot of the singer -- because of the crushed blacks in the background, FPN is clearly visible. Again, that is due to the 4K sensor and is said to be fixed entirely with the new 4.6K sensor. The BMCC didnt have any FPN at all, and I hope the same will be true for the 4.6K.
Sensor: Pros
Now something positive about the sensor. Both the 4K and the Full HD are absolutely beautiful -- when exposed and lit correctly. Outside, for instance. The Full HD seems to have a lot more detail than footage from the BMCC does. The colours are nice too. A bit more contrasty (and bit bit less film-like). Also, I absolutely adore 60fps -- its something we always wanted to do with the BMCC. 60fps Blackmagic footage might just be the best thing ever. I havent shot RAW yet, but will soon. I imagine it being just as good as RAW coming from the big Ursa, as they have the same sensor. I did not think I would like the image coming out of the 4K sensor this much -- but only when we had enough light to work with.