If you're camping, I would suggest panniers: keeps the weight lower. Personally If I'm camping I use my Carry Freedom trailer with a large Ortlieb bag strapped to it: more stable and keeps 70% of the weight off the bike. Not ideal for riding on rougher trails off-road though. However for bivouacking or credit card touring, a saddlebag (plus maybe a bar bag for light stuff, phone, etc.) is probably all you need.
Can recommend the Carradice long flap saddlebags. If your saddle does not have loops, you can fit clamp on loops or a QR block that fits to the seat post.
The huge Camper Longflap (24 litres capacity):
http://www.carradice.co.uk/index.php?page_id=product&under=range&product_id=35
Or the slightly less huge Nelson Longflap (18 litres):
http://www.carradice.co.uk/index.php?page_id=product&under=range&product_id=37
Also the slightly more contemporary fastening Super C saddle bag has a very large capacity (23 litres):
http://www.carradice.co.uk/index.php?page_id=product&under=range&product_id=33
As well as the handy side pockets all these have D-rings on the top flaps which mean you can lash items like waterproofs, etc to the top using toe straps, bungees or leather straps.
If you prefer a seat pack style bag, worth considering something like this Super C SQR Tour (16 litres):
http://www.carradice.co.uk/index.php?page_id=product&under=type&product_id=56
If you shop around on fleaBay you can often pick up cheaper used saddlebags or new factory seconds: I did the latter for most of my bags and really you can't tell there's anything 'wrong' with them: Carradice quality control is exceptionally good..