Tamron 17-50 to CZ 16-80

Hi All

I know this has been discussed at length many times before, so apologies for going over old ground.

Given my lens lineup includes fast primes, I'm finding less need for the f2.8 on my Tamron 17-50 and am thinking about swapping to a CZ16-80 for the added reach and Zeiss sharpness.

Despite this, the question of being able to shoot crisp shots wide open is holding me back a little.

In your experiences, how well does the CZ hold up when shooting wide open?

cheers

E