I am at an impasse with trying the get the DSLR to capture the motion being detected by the RPi. Namely because there is a two second delay between the time the motion is detected by my Python script and when it actually occurred! I have installed 'motion' on the RPi and it also suffers from the same delay. Hmmm. What to do?
I guess I will see what the delay is when using PiggyPhoto to grab preview images. If that looks to be working then I will go back to pondering stability of the DSLR interface across libgphoto2.