photojoern.de said:Quote: "I should have used a smaller aperature and a slower shutter speed."
I think this summarizes very much it. The light was just too little. If you work with aperture 1.2 and 90% are out of focus, then it´s low light or your technique or your AF settings. But I doubt that there´s a better camera AF system than the 1DXII or 7DII from Canon.
ISO51k is probably pulled too much. Post processing can fix some of that, i.e. nik software collection with lightroom.
Equipment wise I would not worry too much, rather work on focussing settings and technique and try ISO12k, which gives reasonable to good results, in my opinion.
Focus settings or hand held technique would not have helped at all. 50mm @ f/1.2 ******* the whole shoot.
The unfocused images were a depth of field problem, thus, a knowledge problem concerning the effect of f/stop on depth of field. I learned this the hard way too.