focus issues - new SEL70200GM f2.8

[terfarr78]

firstly lol very new to photography and learning - so it may just be me  - i have an a7riv - i am having issues with focus with a new lens 70 - 200 f2/-8 - at first i wondered if my lack of knowledge and skill but i have used the 100 - 400 and also recently 24 - 70 f2.8 and although not perfect i have had some great sharp images - but for some reason with this lens the photos are terrible - even i can't have got worse lol - in manual - raw - af-c   - wide focus area for the moment but have started using back button focus - i am a novice so i could be just doing something wrong - i am watching and following all videos and tutorials - can anyone just let me know what i am doing wrong or can lens have faults thank you  - xt

[Peter_S.]

Hi terfarr,

Hmm, if the pictures with the other lenses are fine then you should do everything right.

Maybe the 70-200 is faulty.

Have you tried to focus manually?

What is the shutter speed? Usually you should use a shutter speed of 1/focal length (e.g. focal length is 200 mm then shutter speed should be 1/200).

Cheers

Peter

[terfarr78]

thank you for reply 
i am new so manual focus would be all new so not tried that yet 
the shutter speed is generally between 200 - 800 at the moment as only minimal movement
i hope lens not faulty as literally just got last week lol

i am wondering if i have done something with camera settings wrong - i am attempting back button focus and must admit confused with how to use it  - i hold it continuous which how i have seen it explained and then another video looks like it is saying use it to focus and then release thumb of button and it should now stay focused and follow subject - will have to try both lol - i just want really shape detail images - especially as mostly wildlife or pets - just so confused as both the other lens worked fine until i started trying all the different focus and tracking lol - in wide at the moment - either pet or human eye track not that seems to work either at the moment - had hoped i had af and auto tracking - think i may be just trying to hard lol - but thank you again i will try again and if no joy try and get the lens to the shop - xt