“So am I right in thinking that a deep dream processed image would qualify as “altering an image’s overall content”?
–A deep dream processed image should qualify!
“Curious, how exactly can you tell when something is poorly over processed/ over saturated vs hdr?”
–I can’t always tell, so some of this is honor system. However, an HDR is an image that combines exposures, typically separate frames, so it’s more than one photo combined. That’s different from simply adjusting curves on a single image or oversaturating a single image. HDR sometimes leaves tell-tale signs, particularly halos around areas of contrast (e.g. lighter areas around trees against the sky).
“I assume stitched panoramas are out, but what about the “art filters” on digital cameras?”
Stitched panoramas would fall into the category of combining separate photos, so yeah, not for this contest. Art filters that are applied to a single photo on a digital camera (as opposed to combining separate photos) should be fine for this contest.