Photos taken in connection with employment is the major except to copyright ownership, and employers' rights are much more extensive than you might think.
The key phrase is 'in connection with employment' and this can extend outside working hours, away from the normal place of work, and to situations that you might think are nothing to do with work. Works outings, xmas party, that kind of thing - all potentially employers' copyright, though there are no absolute rules (that's what courts are for).
99.9% of the time it makes no odds and nobody gives a damn anyway, but if push comes to shove and it goes to court, you could well find yourself on the losing side.
The first question is, are you a formal employee, and not a freelance? If your employer deducts tax PAYE, then you probably are and your copyright could be vulnerable.
The other question to ask yourself is 'would I be in a position to take these photos if it wasn't for my work?' If the answer to that is no, then your copyright could be in jeopardy, but if you take care not to upset anybody, or use the pictures in a way that might cause trouble (eg Facebook, sending commercially sensitive stuff to magazines etc) then you'll be fine either way.
