Check your render mode in Tools panel of Home ribbon:
“Change your render mode to “Presenter” and you can switch back and forth between “Perspective” and “Orthographic”.”

Original post:
http://enceptia.com/orthographic-mode-navisworks-gone/#more-2981

via
https://twitter.com/MattDillon78247/status/431192923971923969

Awesome post from Klaus over at:
Revit and Camera Match / FOV and Focal Length

He provides a family file and a step-by-step process for how to match a Revit 3D perspective view with a real life camera photo. There are some nice implications to this, especially if you want to use a real life photo as a background for a rendering or other visualisation. Thanks Klaus!

Note:  his post relates especially to a Canon EOS1000D (some tweaking may be required for other cameras).

via
RevitForum Blog: Best posts of the month of May 2011

As we all know, Revit really wants you to be able to properly visualize your building. You may have experimented with Section Boxes in normal 3D views, but you can also use them in Perspective/Camera views.

  1. Make a new Camera View.
  2. Go to the View Properties of the Camera View, and select ‘Section Box’
  3. To modify it, select the Section Box and then switch to a Plan View. The Section Box should still be selected, and you can modify the grips (you can modify these grips in many views).

Using this technique, you should be able to make some awesome cutaway views. These views can really help you to visualize and optimize your design.