Just had a look at these Cokin Filtershttp://www.filtershop.com.au/
I can understand a bit more now by looking at these diagrams etc.
Looks like a great set up.
So I need to buy adaptor ring,filter holder.and then the filter to slide in.
What filters are you guys using around sunset,just after sunset?
Also I can see what Humayan means by just holding the filter over lens.I got the impression that he felt this more desirable,-what's the reasoning here.
I hope to get to get to a photography shin-dig and see this gear before I purchase.
In the mean time I have been studying HDR-looks great!,and DDP have ND8 filters for $50 (77mm) at present.
Thanks everyone for help
Chris