Dave, I think you misunderstand the reason why I undertook the project. The D40 does not have auto-bracketing for use in HDR photography. HDR involves taking multiple captures of the same subject at different exposures. I'm using the RPi to control the D40 to take a photo, change the exposure, take another photo, etc. Yes, I could use the remote to do this but changing the exposures requires touching the camera which means the position of the lens will move. Even the smallest change messes up the HDR .

Here is a great tutorial on HDR photography: http://www.stuckincustoms.com/hdr-tutorial/

If the D40 had auto-bracketing I would have no use for the RPi for this project. The other project I mentioned in the blog post is using the RPi to trigger the Nikon at intervals for time lapse photography. I don't want the camera to tell the RPi to do something. I want the RPi to tell the camera to do something.