As far as I can remember kit lens usualy ment cheap and average lens. Of course they are some exceptions and some kits are really good performes. So how good is Sony FE 28-70mm F3.5-5.6 OSS which is sold as kit with full frame Sony E-mount cameras. If you think about buying one as a cheap walkaround zoom then this short review may help you decide if it is worth it.
Lens is really small and lightweight for a full frame zoom. It weights only 295 grams which is great if you want to travel light. It has barely noticeable light fallof. At F3.5 and F4 we have really, really light vignetting which reaches mid sections of image. At F5.6 it gets even less noticeable and remains like that to F22. Excellent result. Color rendition chart show slight greenish tint and suspicious brightness. It seems that lens is producing slightly brighter images than all other 28mm lenses I’ve tested using same camera settings. Perhaps there is some in-camera processing happening due to full electronic control over the lens. Just FYI – all possible in-camera processing functions are always disabled in my test. No DRO, HDR, lens compensation, color profiles etc.
Sharpness in center is excellent from wide open however mid sections and corners are a bit softer (but still sharp enough to say they are good). Stopping down to F4 doesn’t change much, but at F5.6 mid sections sharpness is excellent with very good corners. From F8 to F22 only extreme corners are getting a bit better but still remain a bit softer than rest of image. Overall performance is very good, way better than most of legacy primes and not that much worse than Carl Zeiss 24-70mm F4 zoom. Lens also have very good distortion controll and beats Zeiss zoom in this aspect. There is really slight barrel distortion visible especially in uppper right and lower left corners but nothing to worry about. In most shots you may skip distortion correction. Again, excellent results.
Given the lowest price tag of about 110 euros for used 28-70mm kit lens against 550 euros for used Carl Zeiss 24-70mm F4 zoom the choice seems obvious. But is it that obvious? Zeiss is great if you need 24mm at wide end or constant aperture across entire zoom range. If those are important for you, go ahead with Zeiss. Otherwise you may consider getting Sony 28-70mm kit and spending saved money on other lenses, ie. some primes.
June 14th 2019 update. After testing this lens in various conditions I found following issues that change my final verdict. Short version: if you can afford it go with Zeiss 24-70mm F4.
Long version… It seems that lens is prone to shake despite stabilisation. You may find “shaken” photos even at times like 1/125 sec and no, it is not my fault as I can get perfectly fine shot with Zeiss at 1/15 sec. Additionally lens performance drops under some conditions. Don’t count on decent sharpness with lots of small objects like grass or tiny leaves. Sharpness also can get worse when there is huge distance between you and subject you focus on with central points. When distance is smaller sharpness is very good. I like this lens as budget one and if you know it drawbacks you can get pretty decent shots, but if you don’t want to risk your shots to be “unsharp” go with Zeiss 24-70 F4.