Orientation vs. Rotation

[paolobenve]

I am not clear on the difference or specificity of these two tags.

- What is precisely Orientation?
- What is precisely Rotation?
- Do camera makers use both of them?

[StarGeek]

Orientation is an EXIF tag used in images (see the EXIF Tags page). All images from cameras are saved in landscape orientation (wider than they are high) and the Orientation tag indicates what must be done to an image to allow it to be displayed properly. For example, if you took a picture with the camera upside down, the positioning sensor in the camera would know that and the resulting image would have an Orientation of "Rotate 180".

Here's a good page (via Archive.org) that shows how the Orientation rotation works. Note that it uses the raw number that's saved. Exiftool converts these numbers into a human-readable form when extracting.  See the EXIF tags page linked above for the conversion table.

The Rotation tag is more complex. It's occurs in video files. It's a tag that exiftool creates and doesn't actually exist in the file. Instead, exiftool reads two other tags, the QuickTime:MatrixStructure and QuickTime:HandlerType tags, and from these tags, exiftool figures out how the video is supposed to be displayed. See the Composite tags page.

So when a camera takes an picture, it will write the Orientation tag for that image and when it takes a video, it will write the two underlying tags to indicate the Rotation.

These are the two main tags with those names, but there are other tag in different groups that can have the same exact name. These other tags with the same name are often program or device specific.  For example, some Canon cameras write a Canon specific tag called Rotation. (Camera specific tags are called MakerNotes). Some Panasonic cameras write their own Orientation tag. MakerNotes tags like these are almost always ignored by most programs.

You would use the command in FAQ #3 to see any duplicate tags and the groups they belong to.

[paolobenve]

thank you for your explication.

So I deduce that EXIF:Rotation never exists. Does it?

is there an EXIF:Rotate or QuickTime:Rotate tag? if yes, what is it?

[Phil Harvey]

So I deduce that EXIF:Rotation never exists. Does it?

Correct.

is there an EXIF:Rotate or QuickTime:Rotate tag? if yes, what is it?

No.  StarGeek already explained this.

- Phil

[StarGeek]

So I deduce that EXIF:Rotation never exists. Does it?

is there an EXIF:Rotate or QuickTime:Rotate tag? if yes, what is it?

You can follow the links I gave to the tag pages to see what tags actually exist. You can also download the entire tag list in a PDF under the Additional Documentation and Resources section. I use this PDF to check the existence and location of any tag I'm not sure of.