Back focus adjustment / accurate focus across zoom lense barrel.

[Robino_J]

I noticed yesterday that my Tokina 11-16 is not sharp at infinity. Also the Canon zoom 16-35 L is not holding focus across the barrel.

Is my back focus off and if so where in L.A can I bring my cam for a pro back focus adjustment?

 

[Jon Thomasberg]

Canon 16-35 L doesn't hold focus across the zoom range. Same goes for much of the 'stills' Canon glass (e.g. 24-70, 24-105, 70-200). Can't speak on the Tokina, as I dont have one.

 

[Jacek Zakowicz]

Canon 16-35 L doesn't hold focus across the zoom range. Same goes for much of the 'stills' Canon glass (e.g. 24-70, 24-105, 70-200). Can't speak on the Tokina, as I dont have one.

I have a different experience. They all hold reasonably well by the cine standards. But then again, I have the experience and the tools, I do this for living (fix lenses)

 

[Peter Majtan]

The easiest way to be sure if you have a bad apple of a lens is to mount it on a Canon EOS body and check if it holds focus there. Especially the 70-200 should hold the focus extremely well. The others should too. If tey do on the EOS DSLR, ten your back-focus is off. If they don't - you might have a bad set... Your back-focus might still be off, but it is hard to tell at this point...

Peter

 

[Dimitri Luedemann]

I have to agree on the 16-35 being a little soft, however all the L primes (24,35,50,85) and the 70-200 are pretty sharp.

 

[Peter Majtan]

Another thing to add is the the ininity marks -especially for wide lenses - are different from the 'normal' infinity mark at the extreme ends of the zooms. On the canons you have a separate orange infinity marks on both the 16-35 and 24-70. Not sure about the Tokina, but I would assume it has to have something similar. If not - try focusing infinity at the mid-range of the zoom (between 13-14 mm) and see if the focus is dead-on...