Apologies if I missed this in the documentation, but how does one change cameras? I read the Elysiun tutorial about adding additional cameras by copying the whole scene and this seems rather cumbersome. Is there any way to switch from one camera in a single scene to another, either while working on a scene or during animation via an IPO? If not, why does Blender even have the option of adding additional cameras? There’s something I’m missing in my understanding of multiple cameras. Thanks for any clarification.
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Thanks. I realize now I could have found it in the documentation if I’d looked a little longer 
. Very much appeciate the kindness of a straightforward answer (unlike some user groups where newbies get berated for “unnecessary” questions).
There is also a trick you can use to have a single camera act as virtual multiple cameras using constraints.
The only caveat is that it probably won’t work with motion blur.
You simply put a ‘copy location’ constraint on the camera and enter the name of an object in the object box that you wish to control the camera’s movement or initial position. Then add a second ‘copy location’ constraint for the camera and enter a different object for where you want the camera to end up.
Next, click the ‘edit ipo’ button for the first constraint, and add an influnce ipo curve in an IPO curve window which varies from a value of 1 to 0 where you want the camera to switch to the second object. (It should look like a square wave curve at the frame if you want the camera to switch locations in 1 frame).
Then do the same for the second constraint, but have its influence IPO curve change from 0 to 1 at the frame you want the camera location to change.
Using a ‘sharp’ influence curve will cause the camera to ‘snap’ from one spot to another in the period of one frame, making it appear as the camera has switched.
Using a ‘smooth’ influence IPO curve can also be used to have the camera smoothly swoop from one location to another.
As you can imagine there are all kinds of combinations you could use with constraint and Influence IPO curves to achieve lots of various camera actions.
Hope that helps.
If there is no smooth panning, it could be accomplished simply by selecting the IPO keys for the camera, hitting ‘T’ in the IPO window, and choosing ‘constant’ from the menu it will display. This means there will be no intermediary frames in between key positions. It will simply snap from on keyed position to the next, once it comes up. You might be able to do this selectively with only certain keyframes, though I have not tried using multiple modes as of yet.
And then, you can of course get more advanced and using the “cumbersome” method of adding an additional (EMPTY) scene, placing a camera there, and linking it to the main scene (“Set” in the render buttons), and then nicely blending back and forth (even with fades, slides, etc.) between the corresponding scene strips in the sequencer.
But oh well, that’s probably beyond the scope of the question 