Back focus often out.
 

Hi,
I have the 13x lens on my JVC111 and lately the back focus needs to be adjusted. Is there any reason for this?

Temperature changes, accidental bumping, accidental movement of the Flange Focal lever instead of the macro, leaving macro engaged accidentally, lock knob not tightened enough, gremlins messing with it when you're not around...

Thanks Shaun,
I must admit it has only been happening lately and could be due to the temperature. It has been very hot in Perth these days and there is no doubt I will have to check it each time I shoot from now on. The camera has never acted like this before. i feel confident that all the knobs were tight. If temperature will do this, it is because of taking it in and out of the airconditioned car into a warmer environment.

Very likely that's it, then. AC to heat (must be nice! It's been -20 celsius here for 2 weeks!) is often enough to throw out the delicate adjustment.

Hey Dennis
 

mate I test my backfocus at start of the day for every shoot, as you know that if you not on your game, you might be the slightest bit out and your shoot looks soft. Especially when like in perth it can 20C in the morning 40C by 4pm, that's a lot of expansion and contraction of metal, not that we leave our camera's in the direct sun of course.