iPad Camera Connection Kit - Photo resolution When I send photos from my PC to my iPad through iTunes, there is a pre-processing stage where iTunes reduces the photo size and resolution (I think).

Does this also happen when I use the Camera Connection Kit to add photos from an SD card? If so, does this mean that I will lose the originals if I delete them from the card?
The iPad Camera Connection Kit is simply a USB hardware interface. It performs no processing and can store raw as well as jpeg from a camera or SD cards. 

The iOS photo app will show you the pictures it can, but of you have an exotic raw camera - it will simply hold the images unchanged to deliver to your computer rather than process or change any images.