In MPC-HC you can do captures through an item of the File menu, or assign a shortcut to it (e.g. I assigned the "P" key)
But so you say that you can read the blu-ray with MPC-HC directly? It was a non-protected disc then I guess Since for blu-ray that I bought I had to use AnyDVDHD to be able to read them with MPC-HC due to the protection.