[Digikam-users] Rename Problem

[Jean-François Rabasse]

On Mon, 9 Sep 2013, Mick Sulley wrote:

> I have set up import to rename pictures based on date and time.  The problem 
> is that it is an hour out.
>
> The rename string I use is PIC[date:"yyyy_MMdd_hhmmss"]
>
> If I run
> exiftool "-FileName<DateTimeOriginal" -d "PIC%Y_%m%d_%H%M%S.%%e" .
> it renames correctly.
>
> I suspect that it may be a GMT vs Summertime problem but I cannot see any 
> settings for that in Digikam.
>
> Any ideas/suggestions??

Hello Mick,

I happen to have datetime related problems too (not when renaming files,
I don't use that, but when geocorrelating images).

Date and time raise regular problems (and will always do), because of a
historical mistake in the Exif standard.
Timestamps encoded in Exif sections of images use a 19 characters text
field. This is Ok to encode 'YYYY-MM-DD HH:MN:SS' but, too bad, people
elaborating the Exif standard forgot the timezone.
(And/or forgot to specify that this should be UTC.)

So, the common usage is to consider the camera clock is setup to user's
localtime, and application software consider that the timezone is the
one of the current computer.
This works in 95% of cases, but becomes false for people that travel a
lot.

To work around that missing info, most cameras manufacturers provides
setup functions in the camera, to specify the date and time, but also
the timezone and daylight savings.
As this information cannot be written in the Exif data, Exif standard
is more or less locked now, they put that in the non standard Maker
Notes section.

For example, for Nikon Makernotes, one can have things like :
   <Nikon:Timezone>+01:00</Nikon:Timezone>
   <Nikon:DaylightSavings>Yes</Nikon:DaylightSavings>
(France, summer time)

But not all application software decodes and use Makernotes to adjust
timestamps.
Exiftool does ! That's probably why you get correct values using it.
Digikam uses the Exiv2 library, and I don't know if Exiv2 does that
kind of processing. Maybe someone knows ?

Anyway, what you can do is :
1. Check your camera settings, date, time, timezone, daylight savings.
2. Check your images files, e.g. with exiftool, to see if timezone
    info is exported in Exif Maker Notes.
3. Check if your computer timezone and daylight savings is consistent
    with your camera.
4. If something is wrong, hem, don't know. I doubt Digikam provides
    some sort of setting, because it's not an application setting but
    a « per shot » setting.
    But I may be wrong...

You can also check the creation date of your images in Digikam folders,
Informations, Metadata. If it's correct, this sounds like a bug in the
rename function. If it's shifted, should rather be a decoding problem
in the Exiv2 library.


Regards,
Jean-François