A large family gathering or a group of friends at a picnic or other social gathering somewhere in the mid 1960s.
There are a large number of people in this group – I counted thirteen and there may be others who are hidden behind others in the foreground. I can’t make my mind up if this is a picnic – I can’t actually see any food, but several people are drinking from matching plastic cups which look like they come from a picnic set. The thing that interests me most about this picture is the odd camera the chap in the bottom left hand corner is holding – it’s not one I recognise at all but I think can see it has a large film advance wheel – or possibly, as Mike suggests in the comments below, perhaps this is a large eye cup and it is a movie camera?
The date on the slide mount is July 1966.