Exiv2

As far as the different labels go, exiftool is giving you it's own Composite tags:

http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Composite.html

If you give exiv2 the -pv mode, it will give you the plain value of ExposureTime.

$ exiv2 -pv -g ExposureTime IMG_4810.JPG
0x829a Photo ExposureTime Rational 1 605/10

What does gexiv2 get_exposure_time give you?

I'll just make a small case, hoping you will come back on this decision.

However exiv2 has been presenting data in this form for years and changing it may break a user script.

I notice that if you run exiv2 on images with smaller exposure (not sure when the switch happens. After 1 sec maybe?), you get a rational output:

Exposure time : 1/25 s

So that means that any working script existing out there would already know how to handle rational output. So I propose you always stick to rational output (unless maybe the denominator == 1) and no script would ever be broken. :-)

For exposure time, really half a second is the whole world! You just can't say that 0.5 sec and 1 sec are the same thing when it comes to photographic exposure. No photographer would ever accept such a point. Hence I would say this is an obvious bug. So even though it somehow broke some scripts out there (but aren't they already broken if they show a wrong value? Furtheremore as I showed above, I don't even think any script would break anyway since you already sometimes show rational values), it may also fix a lot of workflow involving exiv2. It would fix ours for GIMP at least.

As Alan has pointed out, the "vanilla" values are correct.

We can indeed use gexiv2_metadata_get_exposure_time () and it does work (I tested right now). And we should probably do so for at least all the standard Exif tags at some point. But right now, there are no special handling codes in GIMP. We just display all the tags with gexiv2_metadata_get_tag_interpreted_string(), which gives us indeed a human readable version of values (with unit added, etc.), without any specific handling of any metadata.

Now I see we could try and get the type for every tag with gexiv2_metadata_get_tag_type(), and if it's a rational we get the rational value. But really that gets us uglier output (it's nicer to have a "F5" aperture display, rather than just 5, or units appended like "60.5 s", etc.). So basically the current exiv2 API does not allow us a perfect "generic handling" of metadata (either we lose accuracy or we lose pretty human readable output).

As a conclusion, I really hope you will reopen this report and fix this. :-)
Thanks!

For reference, the GIMP bug hanging: https://bugzilla.gnome.org/show_bug.cgi?id=711242

Awesome, thanks!