Judging by the brightest part on the guitar and on the curtains it looks like there was enough light to make a better decision and have a pleasant result. 12800 ISO 1/125 sec 2.8?
I would rather do 1.8 aperture, 1/100 ( 1/60 if necessary and it didn't get blurred ) Iso 800 maximum.
IMG_0364 on Low light condition is Not Good enough result.
at ISO 12800 it might looks better than G15 though, i'm not sure. need side by side comparison
who cares? it looks simply unacceptable.