Back focus with extender

[Gungnir]

Been a while since been on here so hello again

Went for a walk around park today trying 2x extender on a 70-200 lens. Everything worked great in good light but it back focused in low light.

Is this normal? Do I just need to adapt to it? Was using centre point only so know exactly where it should have focused.

 

[Phal]

Well low light will making the focusing more difficult obviously But you can microadjust the lens with the TC on.

Guess you need to test it in good light first. If it's fine with plenty of light but suffers in low light then it's not really something that can be adjusted as far as I know.