A7R3 AF-C at infinity not sharp

[pcr1040]

I have a A7E3 and several lenses among them the 70-300 G OSS. I find that many of my images are not in crisp focus while others seem ok. I have had several camera systems over the years and never had this kind of problem then or now with my other camera, a Panasonic g9 and 100-400mm Leica lens.
The 70-300, using AF-C, cannot seem to auto focus to focus on very distant objects (infinity) Almost every single image shot at infinity is blurred noticeably. I am not sure its any better using my Ziess 16-35 f4 lens at infinity. Problem is size of the objects at infinity are really too small to make a critical judgement about sharpness.
If I use manual focus with the 70-300, I get a much sharper image than with AF (set AF-C) and it make little difference how high the contrast in the scene is, they come out blurred on AF-C.
This observation raises a question about images shot at closer range. Is this symptomatic of a general focus error or is it a limitation of the focus system in the A7R3, or finally have I a defective camera?
Using wide area focus with the A7R3, many of the images shot at shorter distance that I thought would be in focus were less that as crisp as other images shot at similar distance.
Bottom line, is this situation indicating a Camera issue that can be fixed, a problem in how I use this particular camera? Or, is it a lens issue with the 70-300 G OSS lens?
I am baffled because I get much sharper images with my Panasonic G9 and the 100-400mm lens that I use for wildlife, than I get from the A7R3, which I use mainly for landscapes.
Any suggestions and thoughts about this issue of mine?

[JCC]

Get a focus target and adjust the focal point.  It may be front or back focusing. 

 

 

[pcr1040]

JCC, thanks for responding to my inquiry concerning qmycamera and focusing it.  After reading your comment I went to the Sony site and looked up their page on Front andBack focus adjustment.  After reading it, I think they are referring to NON- Sony lenses. 

I s this also an issue with Sony Glass?  All my lenses are Sony manufactured, and one of concern is the Sony 70-300 G OSS.   When I look at the camera and the "Micro Adjustment" item in the menu, it is ON, but if I then select lens, it reports "Invalid with this Lens"

So, I am at a loss as to what this all means.

Edited January 18, 2020 by pcr1040

[Chrissie]

10 hours ago, pcr1040 said:

After reading it, I think they are referring to NON- Sony lenses. 

I got also curious when I read @JCC 's suggestion, but came to the same conclusion as you did.

Edited January 19, 2020 by Chrissie

[Thad E Ginathom]

I went from film to P&S to mirrorless, and have no experience/knowledge of the entire DSLR generation , but vaguely remember reading that, as mirrorless focus, being a function of the sensor itself, is always at the focal plane and front and back focussing adjustment is providing for the lenses that use the Sony adapters that provide DSLR-like focusing mechanisms.

[pcr1040]

Thanks to both responders.  I guess I read the information about Back Focus Adjustment as you guys did.  So I am inclined to think the issue is really an issue with this lens.  It seems to sharpen up at 300mm when I stop down to f8.0,  But even then it's really not as crisp as I would like.  In truth I think this is a design issue for most long zoom lenses.  They all seem sharpest at the shortest focal length.  My other system is a Panasonic G9 with the 100-400mm lens and it too is sharpest at the shorter FL.  However, even at 400, it seem sharper than this Sony lens at 300mm.