I am not a pixel peeper. In 17 years I have sent back five new lenses with big problems (optical and mechanical), but I am finding that Sony's quality control is just appalling. The five lenses I have sent back before Sony, are explained as below:
Canon 24 f1.4 L II (would not focus properly).
Canon 24-70 f2.8 L II (box had suffered severe impact damage and lens was decentered on left and would not focus using left focus points).
Canon 40mm EF Pancake (decentered and did not sharpen up in entire lower left quadrant until f8.
Leica 75 Summairt-M (cam not remotely accurately machined and only focused accurately at intinity. As you got closer the error increased to feet.
CV 21P - severely decentered.
So there we go. I have shot Canon for over a decade and have bought loads of lenses and I can only put two returns down to QC. The 24-70 II had evidently been used as a football before delivery. I have bought five Zeiss ZM lenses and all have been good. I have about ten Leica lenses of various vintages and all are optically nicely even, even if part of the deal is soft corners at various apertures... they are evenly soft!
With Sony? Well, not one single lens I have purchased has been good on the first try. It took me three 35mm f2.8 FE Sonnars to get a decent one. It still has one extreme corner that is a bit softer than the others, but its no biggie. Overall it seems very good indeed. My first was horribly decentered on the right side and the second appeared to be really good, albeit with a slightly soft extreme top left.... until I shot from the air at infinity and realised that at this distance, the entire left side varied from OK-sharp to 'so blurry I'd be better off with a 4 MP camera with a good lens'.
My 28-70 FE kit zoom has a fairly bad bottom left corner, but I have decided to live with it as it is OK when stopped right down, where I tend to use this lens.
I decided to buy the 55 f1.8 FE and had fingers crossed, but its pretty awfully ailgned. The lower left is 'milk bottle' sharp and the top right is similar. Neither get sharp at any aperture. The top left and bottom right are super sharp like the centre, picking up noticeably at after f2 and peaking about f4.5.
So, out of a total of five Sony lenses that have been through my hands, only ONE is actually OK and performing to the same sort of consistency I would see from Canon lens. I am not putting these lenses under a microscope here. I am shooting normal stuff and perfectly accepting of imperfection. I am judging things mostly looking at images at 1:2, rather than looking at 1:1, and they are still all over the place.
C'mon Sony, this is ridiculous. If you have a 'Zeiss' and 'G' line of lenses, look to Canon for what is expected at this price point. I am not expecting perfection. I am, however, expecting not be be jerked around with almost every purchase. I am glad I bough from Amazon as they have no hesitation sending me another 55 f1.8 FE, despite sending back two 35mm FE lenses already. Many stores in the UK would simply laugh at me at this point.
To put it in perspective, I bought five thirty year old Canon FDn lenses on ebay and every single one is reasonably centred. This says it all.
Get a grip Sony. This is getting boring. I had been considering the 70-200 f4, but after this, I'd rather just use a Canon with metabones adaptor for landscapes. I just isn't worth the hassle. With Canon, I know the odds of getting a dud are pretty long. Ditto for Zeiss and Leica, but with Sony it seems the odds are reversed. The good ones are rare and the obvious duds are the norm.
I'll be writing to Sony to see what they have to say.