Can someone please tell me how iPhoto deals with folders?

Question

.. or direct me to an Apple paper on the subject.
I have recently come over from Windows where my photo library of 7,000 photos organised under Photoshop Elements simply seemed to have the photos in a single folder. Now I see there are original, data and modified folders all holding more or less equal quantities of files by year. What's going on? If I wanted to use another program to manage the photos such as Aperture or Lightroom would it be able to cope with all this?
iMac   Mac OS X (10.4.9)  

Answer 1

Jadw59
A Note about the iPhoto Library Folder:
In this folder there are various files, which are the Library itself and some ancillary files. Then you have three folders
Originals are the photos as they were downloaded from your camera or scanner.
(ii) Modified contains edited pics, shots that you have cropped, rotated or changed in any way.
This allows the Photos -> Revert to Original command - very useful if you don't like the changes you've made.
(iii) Data holds the thumbnails the the app needs to show you the photos in the iPhoto Window.
Yes you can integrate your iPhoto Library with external editors and other apps. In the case of editors you can set them so that when you double click a pic in the iPhoto Window it opens automatically in the editor or your choice, and saving in the editor again automatically saves the pic back into iPhoto.
In the case of Aperture you can import an iPhoto library straight into Aperture, iPhoto can also read Aperture libraries. I'm not sure about Lightroom.
If you're concerned with finding pics, remember that it all can be done via the iPhoto Window - the is simply never a need to go into the Folders in the iPhoto Library Folder. There are three ways (at least) to get files from the iPhoto Window.
1. Drag and Drop: Drag a photo from the iPhoto Window to the desktop, there iPhoto will make a full-sized copy of the pic.
2. File -> Export: Select the files in the iPhoto Window and go File -> Export. The dialogue will give you various options, including altering the format, naming the files and changing the size. Again, producing a copy.
3. Show File: Right- (or Control-) Click on a pic and in the resulting dialogue choose 'Show File'. A Finder window will pop open with the file already selected.
Rolls in the iPhoto Window correspond exactly with the Roll Folders in the Originals Folder in the iPhoto Library Folder. You can move photos between Rolls, you can rename rolls, edit them, create them, as long as you do it via the iPhoto Window. Check out the Info Pane (wee 'i', lower left) the name and date fields are editable. Edit a Roll Name using the Info Pane, the Roll Folder in iPhoto Library Folder/Originals will also have the new name.
So, not quite a complicated as it seems at first.
Regards
TD