Upside down or sideways photos in Mac OS X

A plausible explanation for those random Upside down or sideways photos in Mac OS X you sometimes get. I figured it was an endianness issue but apparently it's caused a EXIF Orientation flag issue. Software Support for Orientation While there are countless software programs available today that display JPEG images, only a subset of them actually interpret the EXIF Orientation flag. Just like color management, many programs simply display the JPEG image as it is stored, and completely ignore any extra details stored in the file's metadata. The most important of these additional details is the Orientation flag, stored in the JPEG APP1 marker under EXIF IFD0.