I believe Lightroom 5.5 should look for an Exif timestamp if an IPTC timestamp is not found in a jpg.
LR 5 looks in both IPTC and EXIF metadata fields to determine capture date. If you think the Sigma Photo Pro files have an EXIF capture date but LR isn't reading it, please upload a sample to Dropbox or similar and post the link here. We can take a look in detail to see what might be going (and to which manufacturer we should direct feedback).
A related issue: batch timestamp correction ([Edit Capture Time]) should be done in minutes in addition to hours.
It's not immediately apparent, but the Edit Capture Time command can do batch adjustments in days/hours/minutes/seconds. In the screen shot below, 30 minutes and 1 second will be added to the capture time of each selected photo:
For the first, you are right. Although the comparison between SPP 5 jpg and SPP 6 shows that the difference is the presence of IPTC timestamp, it seems that LR 5 does recognize a photo only with an Exif timestamp from another camera.
It means that some other part is wrong with SPP 6.0.2 jpgs.
As for [Edit Capture Time], I meant a batch correction. [Adjust to a specified date and time] only works for a single photo, I guess.
"Shift by set number of hours" is good for time zone adjust, but sometimes one would notice that the camera time is wrong.
Other photo edit tools, for example, PlayMemories Home can shift multiple timestamps in minutes.
If you post a link to a sample SPP 6.0.2 image, I can see what might be going wrong, in particular, whether it's an issue with LR or with SPP.
With Edit Capture Time, the instructions at the top of the window (see the screen shot above) explain how to do a batch correction: Select multiple photos, do Edit Capture Time, correct the time for the photo shown in the window, and the other selected photos will all be adjusted by the same amount.
John, thanks again.
It seems that the instruction at Edit Capture Time differs when selecting a single photo and multiple photos.
I confirmed that multiple timestamps can be shifted.
Here are the photos:
SPP 5 jpg
SPP 6 jpg
I also found that SPP 6 is not yet supported for DP1m cameras. This could be the reason of the timestamp not showing up.
I used the free Exiftool to examine the files (Exiftool is the most authoritative tool for examining the metadata of images). The file _P1M1575-spp6.jpg does contain a capture date:
[EXIF] Date/Time Original: 2014:07:02 16:32:07
However, the metadata structure is incorrect or has been corrupted; "exiftool -v" produces the following warnings:
Warning = Short directory size (missing 236415 bytes) | Warning = Bad IFD2 directory
This almost certainly is why LR can't read the capture date. Smells like a bug in SPP 6 that you should report to Sigma.
Thank you John!
This clear the thing up.
I will send the info to Sigma.
Have a good day!