Well, you can do two ways. Either way works fine.
You can hit Tab to "disengage" the camera and go into Freemode. Use the + and - on the numpad to move in or move out with the camera. Also use the W,S,A,D keys on the keyboard to move the camera around.
A camera mod will do that too without having to use Tab sometimes. Using Tab is just convenient to take screenshots without the UI panel and red pause line (if you use Beosboxboy's mod from Misc. Mods & Careers section).
I use Gunmod's
Camera Mod 3.1 from MTS2 that works fine with Mansion & Garden. You have to read the instructions and install where appropriate. He offered a few flavors that lets you zoom in with objects fading or not.
BUT there are other camera mods that do a great job too. In fact, some of them were based on Gunmod's original camera mod at MTS2 too.