Originally Posted by
Tannin
Turns out it is not odd-ball, it is standard. Apparently, I have never deleted images in-camera on the 1D IV before, only on my various and motely other cameras.
With any twin-card setup in any Canon camera, in-camera delete only deletes the image on the active card. So if you are (e.g.) shooting raw with the CF card as #1 and mirroring to the SD card for backup, delete will axe the copy on the CF card and only that copy. When I shoot raw + JPG, sending raw to the CF and JPG to the SD, delete only axes the JPG, leaving the raw on the other card alone.