Hi @PaulGardiner,
You can achieve this doing the following workflow:
1. Use the Export Attachments toolbox to export the photos to different folders by field value.
2. In windows explorer, search for the photos (e.g., "ext: jpg") in the folder containing all the exported folders. You will get a list of all the photos from all the folders.
3. Select all the photos, cut and paste into one folder
4. Delete all the empty folders
The other replies to your post are using the base script provided by Esri (which is also found in my toolbox as Export Attachments From Table). That script doesn't and can't access the field value because that value is not stored in the photo attachment table, but only in the parent Feature Class. To access this value the script needs to match each photo's REL_GLOBALID to the parent's feature class GLOBALID, which is what the Export Attachments toolbox does.
Hope this helps,
Uri
If this answer solved your question or if you found it helpful please mark it accordingly to help others who have the same question.