As I understand it, the raw file appears in iPhoto as both a raw file and a tiff that is used for display (in addition to the separate jpg created by the camera).
No it doesn't.
If you import a Raw it's copied in and a jpeg preview made of it. There is no tiff involved. If you shoot Raw+Jpeg pairs then you get duplicates. Shooting Raw+Jpeg doesn’t make a whole lot of sense in this case.
When editing the raw file, it seems that the changes are saved in a tif that is *much* larger than the original
It's only saved as a tiff if you have chosen that option in the iPhoto -> Preferences -> Advanced. Otherwise it's saved as a Jpeg. A tiff - as it's uncompressed - will always be a lot larger. That's in the nature of tiffs.
When working with Raws and an external editor again there are no tiffs involved unless you choose there to be:
iPhoto does not handle this gracefully and it's a bit of a kludge.
First off set your preferred app as an external editor in iPhoto:
Note that iPhoto sends a copy+ of the file to Photoshop, so when you save be sure to use the Save command, not Save As... If you use Save As then you're creating a new file and iPhoto has no way of knowing about this new file. iPhoto is preserving your original anyway.
Next: In the iPhoto Preferences -> Advanced, elect to use Raw with your External editor:
Now when you go to edit the Raw it will be sent to your external editor.
Now for the kludge:
You cannot save a Raw. The work you do must be output to a new file, in a new format (jepg, tiff, whatever). However, as the External Editor is making this new file iPhoto has no knowledge of its existence. Therefore you must save it to the desktop and then import it back to iPhoto as a new file.
This means that you will have your Original Raw and the processed version in iPhoto but they will not be recognised as version and original. iPhoto will see them as two separate shots.
So, again, there are no tiffs anywhere in either workflow unless you choose to make them.
Thanks for the reply. I should clarify that I did set the Preferences to 'save edits as tiff', having read that tiffs are the best way to maximize quality. I was just surprised how the file sizes ballooned when I edited the raw photos. For comparison, a raw photo as edited in iPhoto yielded a 102 mb tif; when edited in PSE it yielded a 16mb tif. That seems like a huge difference--I thought I was doing something wrong, or perhaps that iPhoto was playing fast and loose with my hard drive space.
I may have been overly cautious in capturing the photos as raw+jpg, but I thought it prudent to have a backup and version that was easy to share if it didn't need further work. But perhaps that approach doesn't make much sense, if iPhoto just creates a jpg version anyway (even if it looks like just one file). And from what I've read elsewhere, it seems like iPhoto never overwrites the raw file, there's always an original master to go back to.
It does sound like there's no way to work with raw files in an external editor without having to go reimport the file--and is it normal that the raw file keep duplicating itself whenever I do use an external editor? This seems like a waste; is Aperture any smarter about it?
iPhoto never overwrites any original file.
Here's the problem you have: You're using a Raw processor that is also your organiser, but you're determined to use a different Raw processor. Why? The problem disappears if you use iPhoto to process the Raws. The same answer for Aperture.
Or process the Raws prior to importing?