[Hampshire] Rsync question

I have two external USB drives, one holds all my digital pictures and MP3's
and the other will be acting as a backup.

I am backing up the folder /mnt/sdb1/ but there is a folder that I want to
exclude called zunk (it is network wide folder for dropping files for other
PC's to access), so I tried to use the exclude option in my command

rsync -av --exclude=/mnt/sdb1/zunk /mnt/sdb1/ /mnt/sdc1/backups/

but it did not work it still copied files over from zunk (the rest of the
command worked as I intended)

When I wrote my command I found the exclude command on a web site, but I can't
find the site now, but I based it on what was on this web site (I seem to
remember it was excluding a single file)

I have read the man pages and the it lists it as

--exclude=PATERN (or -from=FILE, meaning a file that holds the pattern you
wish to exclude)

Am I barking up the wrong tree with my interpertation, or is there another
way?

While not as important at the moment, I want to delete files from the
destination location that are no longer in the senders location, I was
thinking of using the

--delete-after

Will this do what I want, I assume I put this after my exclude option??

Thanks in advance

Tim