It seems like most, if not all crews had a crew photo taken at some point.  Was this something official - one of the things that had to be done, or was it something that crews just liked to do.  I have seen some photos with info written across the bottom, so I would guess that they are more likely to be official than not.  This is however not the main point of my question.  Does anyone know at what point these photos would have been taken?  Was it when a crew finished their time at the OTU, or would it have been when they were done at the HCU.  Maybe it was when they first joined a squadron, or maybe there was just no rule of thumb, and these photos could have been taken at any time.  Any help please would be appreciated.