I own the xperia z and rx100. Though it's clear xperia z camera is far far far from the excellent quality of my rx100, it wasn't as bad as it appears to be in this test. Mine was the newest firmware, and under bright lights they gave pleasing details, colour rendition and high DR for a camera phone. Albeit the video quality was soft compared to the amazing RX100 video capability, it's not THAT shabby. So I really don't know what you are talking about when you refer this as 'horrible' in terms of IQ. It certainly look comparable to iphone 5 photo quality in general lighting conditions.
I supposed if you measure quality with numbers like the DXO indices, then xperia z comes up short. But look at real world comparison. One notable reviewer from Australia (his youtube name is blunty3000) made a side by side comparison. Though i definitely won't say xperia z is in any way surpassing iphone5, but the short he made and the video side by sides look comparable to me...
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