Photo Metadata Editing / Editor

Solution 1:

The quintessential photo editor that uses folder structure is Photo Mechanic from Camera Bits - it's a professional workhorse designed for triaging 10,000 photos in a weekend and priced accordingly.

It stores all metadata in the images using industry-standard and cross-platform metadata fields and formats. It's highly automated and highly optimized for speed in rendering images to screen and rapidly moving through images for bulk tagging and classification.

Automator lets you make droplets to bulk edit photos, so you might start with that and move up if you find yourself spending more time or money on making a tool than it would cost to buy a tool.

For an example of the power of automation on OS X - check out this workflow. It explains how to use scripts and photo metadata fields that Finder and OS X support out of the box:

• https://macosxautomation.com/automator/showlocation/index.html

Solution 2:

A few years ago, I pointed a photographer friend to ExifTool, a free, command-line based metadata editor. It looked pretty powerful and it did what she wanted. I haven't used it myself, so YMMV.