[HDR-photo] XMP sidecar file for HDR images - Does it make sense?

[Royce Howland]

I like the concepts discussed so far around the HDR XMP sidecar file. 
For me, the least useful data would be pointers back to the original 
source files since I don't keep the input TIFF's once I've worked the 
HDR image to a certain point. Currently the main files I keep include 
the original RAW images, the HDR file (usually EXR ZIP format), and a 
final Photoshop working file (16-bit TIFF with all layers). Plus all 
sidecar and project files from any tool along the workflow. I can see 
the benefit of keeping the pointers to the originals for some people, 
sort of like a project file in a stitching application. I just wouldn't 
use it much myself.

The other proposed ideas for the HDR sidecar sound very useful. In 
particular I'd welcome a good set of core EXIF data, color and profile 
information, and add IPTC data to that list as well since we're just 
brainstorming. :~) One goal for my workflow is to have tools that 
preserve standard metadata and color space across each stage in the 
workflow. I do not like having to re-enter, re-tag or edit important 
things that I have already applied at a previous stage. Right now 
essentially all of the metadata vanishes across the HDR merge step, in 
the general case of working from a previously merged HDR file. It would 
be great if an HDR file browser showed the important metadata that was 
in the input files, and if tone mappers would generate new files 
containing that same metadata.

By default I would recommend keeping the tone mapping settings in the 
same sidecar file with all the rest of the info, in an 
application/operator specific segment. It will change while the other 
metadata will not, but that's not a problem that I can see. Keeping 
metadata and settings properly associated with their base files is 
challenging enough as it is right now, the more sidecar files exist the 
more difficult it becomes.

The biggest benefits of the sidecar would accrue if it became adopted by 
many/all of the major HDR tool vendors and HDR-aware image browsers. 
Failure to adopt the same sidecar standard is the biggest single barrier 
to the idea that I can see.

I do like the current Photomatix capability to save tone mapping 
parameters in an arbitrarily named XMP file (or any other format), and 
would want to see this preserved. This has nothing to do with the main 
sidecar, or with the need for multiple vendors to adopt the same format. 
Much as with the filter settings files in Photoshop, I often use this to 
create some basic "styles" that I can quickly load up for any image, and 
then modify as required. It's okay for this to be proprietary to one 
application.

Royce Howland
Calgary, Alberta