Prevent the loss of EXIF using imageCache does not work
Drupal (7 by itself, 6 via ImageCache) uses GD library. GD cannot handle EXIF, so if EXIF are ever kept during operations, it's more by accident than by design. If you need to keep EXIF, either avoid any processing based on GD (and that means any Drupal and ImageCache provided operations, both in Drupal 6 and 7), or save EXIF to text field on first upload, for example with EXIF Custom, and then add it back on download.