As far as I can tell this should be considered a bug, but please inform me if otherwise.
Issues outlined here seem somewhat related to those I spelled out in this thread I started two years ago. Using Dopus v12.20 now, in Windows 10 Pro 1903 x64. I’m basically continuing experiments with metadata using DOpus and ExifTool. As in the older thread linked to above, I started out with a fresh, blank 1-bit PNG with no metadata, created in PaintShop Pro, then manually added a number of metadata fields via DOpus, then used ExifTool to export all EXIF/IPTC/XMP fields to JSON to see where the information I added via DOpus actually went. The DOpus Set Metadata fields I added in this case were:
Authors: <authors>
Copyright: <copyright>
Description: <description>
Instructions: <instructions>
Subject: <subject>
Title: <title>
Camera make: <camera make>
Camera model: <camera model>
Creation software: <creation software>
Date digitized: 11:59:59 31-Dec-2019
Date taken: 00:00:00 01-Jan-1900
GPS Altitude: 1
GPS Latitude: 2 3 4 N
GPS Longitude: 5 6 7 W
Lens make: <lens make>
Lens model: <lens model>
Rotation: 0
Comment: <comment>
Tags: <tags>; <tag1>; <tag2>; <tag3>; <tag4>
In all cases that I know of, when I’ve added and applied content to all these fields, the date I entered into Date taken was added to XMP:DateTimeOriginal, EXIF:DateTimeOriginal and IPTC:DateCreated, and the date I entered into Date digitized was added to XMP:CreateDate and EXIF:CreateDate. At one point today, I only added Date taken and Date digitized via DOpus Set Metadata, which resulted in only the EXIF date/time fields being added. Subsequently adding all the other fields as listed above did not result in the XMP:DateTimeOriginal and IPTC:DateCreated fields finally being added, though modifying both dates/time fields in Set metadata did. I’ve been able to reproduce this with the same blank starting PNG, and with several other PNGs. Any idea what’s up?
Also, I was trying to use ExifTool to modify the existing content of IPTC:DateCreated and XMP:UserComment, as originally set via DOpus, but got errors. Upon further research and inquiries made at the ExifTool help forum, I learned that the official IPTC specification limits IPTC:DateCreated to date only, while separately specified field IPTC:TimeCreated is intended for the time component. Similarly, the official XMP specification defines XMP:UserComment as a lang-alt-list, rather than a straight text string as DOpus apparently writes it. Because of these, I’m unable to use ExifTool to modify the existing content, or to write new content in the existing format.
Please let me know if it would be useful for me to upload the wayward PNG, and/or maybe the pre-metadata version of it, if you can’t reproduce these results independently.