Select rows which are not present in other table

I've got two tables:

login_log :: ip | etc.
ip_location :: ip | location | hostname | etc.

I want to get every IP address from login_log which doesn't have a row in ip_location.
I tried this query but it doesn't work:

SELECT login_log.ip 
FROM login_log 
WHERE NOT EXIST (SELECT ip_location.ip
                 FROM ip_location
                 WHERE login_log.ip = ip_location.ip)

ERROR: syntax error at or near "SELECT"
LINE 3: WHERE NOT EXIST (SELECT ip_location.ip`

I'm also wondering if this query (with adjustments to make it work) is the best performing query for this purpose.