I took my D7500 out today with my AF-S NIKKOR 17-55mm 1:2.8G ED Lens.
Before leaving the car i cleaned the front of the lens with ROR residual oil remover and a visible dust cloth.
The day was cold but sunny. I had my camera around my neck all the time.
The first few photographs i took were fine.
We then took a walk through a wood by a stream.
When i went to take a photograph i noticed the fogging / condensation.
When i tried to wipe it off i noticed it was inside the lens.
Luckily after a couple of hours inside the house the condensation has gone.
What caused this (could it possibly be the liquid cleaner somehow getting inside from the edge of the glass) and
How do i prevent it in future.
I am rather paranoid about this happening again and have put my 18-105 kit lens in my bag just in case.