Basic questions about Cokin Filters

[Dweller]

if I understand Cokin system filters correctly they are square and fit into a holder that threads onto the lens.

So, if I have a holder for a 56mm lens and a 52mm lens then I could use the same filter on both right?

Do the filters just lay in the holder or are they secured somehow?

 

[SWFLA1]

you are correct - to use the filter holder on different lenses, you simply need the correct adapter rings... the filters slide into the holder. I've never had one fall out, but they are only held in by pressure points..not real secure, but not bad.