DNG Conversions and Time Zones

[samdring]

Just thought I would share the results of some digging I had to do when a problem arose.
I shoot Canon raw so this might not be applicable if your camera records a time zone (or offset)
1. Using exiftool, I determined that downloading CR2 files showed no field or entry for TimeZoneOffset (TZO) in exif.
2. On conversion to dng, a field, TZO is created in exif which has an entry of 0 0 for GMT and 1 1 for GMT +1 hours etc. The spaces in 0 0 etc are intentional.
3. Nothing wrong with that so far except that because Canon (many others?) has no field set by the camera for Time Zone, Adobe (in their undoubted wisdom!) take the TZO from the computer time and zone.
So the effect of this is that having converted all my raws during this autumn (and straddled the BST change at the end of October) a raw taken in Cyprus at GMT + 2 hours converts to a dng with a TZO of either 0 0 or 1 1 dependent on whether the conversion took place pre or post the last sunday in October.
'So what' I can here you say, 'TZO is only meaningful if you want to synch across more than one time zone'. 'Not so' replied I with alarming alacrity, Lightroom among other apps, changes the time of Date Time Original etc when the computer time zone or Summer time changes'.
Moral: Never trust a Dobe Wallah

[grantp]

Interesting.

You reminded me that I had not reset the clocks on my cameras so ...

My Pentax Optio S 5i has a timezone setting and DST offset. The tiome was actually correct.

Canon Ixus Wireless. Double TZ setting and DST offset. Time was wrong showing +1hr.

Canon S3 IS. Double TZ setting and DST offset. Time was wrong showing +1hr.

Canon Pro1. No DST offset, no TZ setting. Time was wrong.

Canon 400D. No DST offset, no TZ setting. Time was wrong.


So, the jpeg devices record TZ (?) and the RAW capable devices don't.

I assume the Optio was showing the correct time because I never got around to changing the DST setting earlier in the year ...


Grant