gphoto2 download command?

[Bob Goodwin]

Can someone give me the proper command to retrieve images from a camera 
using gphoto2?

I used it casually once before to see that it worked and now that I have 
a few pictures I want it refuses to give me an image.

It will provide .ppm and .raw files apparently but the only ones that do 
anything are the .ppm and all I get is some colored lines?  I've gone 
through man pages and whatever else I can find but I am not sure I'm 
using the correct command to download the images from the camera.

Thanks. 

Bob Goodwin