P: Can't clear caption in JPEG exported from master imported with a caption

HI Mark,

I happen to have an Olympus and Nikon cameras handy that always (the Oly) or optionally (the Nikon) set ImageDescription, Artist or Copyright, and I will try this in Camera Raw 6.4.1, first with camera original JPEGs, and saving out JPEGs.

This may be Lr specific, but we'll see! The way to I will try to reproduce this w/ ACR (I think) is to edit the property in Bridge's metadata panel, then open in ACR and use the Save Image feature. In this case two different operations occur. First, ACR works as a "Changer" (in MWG terms) and should update the file. Then when we open the JPEG in ACR to save a new JPEG, it's acting as a "Creator." I would expect the property to be deleted in the first step, and not to magically reappear when create the new, derived, file. It's a bit trickier in Lr, because one has to test at least two cases: forcing Lr to write-back the metadata edit before Export and leaving the orignal unchanged before export. Also, it's important to try this using different Export options to see if that makes a difference.

The new metadata engine in LR 3.4 does not gracefully handle the case where a metadata field is populated in the original source file, but a mapped metadata field is empty in Lightroom's Metadata panel.

By "mapped metadata field", I mean the fields which are represented in two or more of EXIF, IPTC/IIM, and XMP. See the chart on page 21 of MWG guidance 2.0. Examples:

• 
  
• EXIF ImageDescription, IPTC Caption, XMP dc:Description
• 
  
• EXIF Artist, IPTC By-line, XMP dc:creator
• 
  
• EXIF Copyright, IPTC CopyrightNotice, XMP dc:Rights

To recreate:
(1) Import a file that has a value in a mapped metadata field. Many cameras can put something in EXIF Copyright, EXIF Artist. Some, such as many Sony and Olympus cameras, always (and rather annoyingly) put something in EXIF ImageDescription.
(2) In Lightroom's Metadata panel, note that this original data has been mapped to the corresponding fields as expected.
(3) Empty those fields.
(4) Export the file.

Expected behavior: The exported file should have nothing in all of the mapped fields or the fields should not be present at all.

Actual behavior: The original EXIF field is still present with its original value. The mapped fields are not present.

This is incorrect -- the guidance says that they should be mapped together, but Lightroom is creating files in which they are not.

Also, the guidance says on page 29, "A string property that is comprised of only spaces or only nul characters MUST be treated as non-existent." I think it's likely that this phrase is meant to be considered by the Consumer, not the Creator/Changer -- but I think it's reasonable to consider that the now-empty UI field is a meaningful value that should be mapped to all corresponding fields.

This is only a problem for mapped fields. In cases where LR does not present a mutable field in the Metadata panel, it makes sense to copy the data from the original to the export.

FWIW, LR 3.3 handled this correctly, which made Olympus and Sony users much happier. They could apply a metadata preset on Import which emptied the Caption, so the annoying camera-generated value was not present on export.

I suspect this problem also exists in Camera Raw 6.4, but have not verified this. It also probably doesn't happen in Lightroom if Limit File Size is checked when exporting JPEGs, because Limit File Size doesn't use the new metadata engine.