The Photos Mac OS app is great to use to manage photos all in one place including editing photos until you are unable to access the actual photo files. There are several ways in locating them and I think this is the easiest, manual way of doing so. Here is a step-by-step process on how to locate photo files on Mac OS computer with screen shots.
How to Access Photo Files on Mac OS:
1. Open the Photos App (from bottom menu or from Applications in Finder):
2. In the top menu bar, click on “Photos”; then, click on “Preferences”:
3. Click on “Show in Finder” option in the General tab of the new window that opened:
4. Then, right-click on “Photos Library”:
5. In the drop-down, click on “Show Package Contents”:
5. And, lastly, click on the “Masters” folder to access all of your picture files organized by year and so forth.