Short answer: they are only able to log the hosts you visit (e.g. security.stackexchange.com, google.com, etc) and not the full address (e.g.
https://stackexchange.com/login). If you access unencrypted webpages (
http instead of
https), they are able to see everything. ISP are not known to log unencrypted webpages en masse, but I wouldn't not be surprised if the NSA or china logs this kind of meta information.
Since DNS traffic is not encrypted, your ISP could see every host you visit (it does not matter if you use Google's DNS or theirs). If you visit
https://security.stackexchange.com/questions/ask (note the
s after http), your ISP will see that you visited
security.stackexchange.com and that you used HTTPS. If you use HTTP, the will see everything (the content of the webpage, url, and sometimes even cookies. Note that
security.stackexchange.com will always redirect you to their HTTPS version. This means your ISP will only see that you were redirected to the encrypted version. If you are not on the https version, you're being MITM'd. You should then use a VPN).
If you request
http://security.stackexchange.com/questions/ask (as you have originally asked), your ISP will also be able to tell that you requested the very page since it is not encrypted. It does not matter that Stack Exchange is redirecting you to the encrypted version because the you have already access the unencrypted version once. Make sure you always use
https when possible.
If you access google via
126.96.36.199 (one of their IPs), your ISP will still be able to see that you visited
188.8.131.52. Since your ISP is also probably running a DNS server, they could also check where
184.108.40.206 resolved to (which will probably return google). They could also check that by hand, but this would take more time.
The only way to protect you from these attacks is if you use a VPN. Note that by using a VPN you simply shift the trust to someone else. If you use a public VPN, there are many more parties who can monitor your traffic: the VPN provider (their server might log everything you do), the server host, and the government the server is located in.