iPhoto always opens the last library opened so each time you Option Launch iPhoto and choose a new library you will use that library you option launch again
And to open the same library with different computers they both need to have the same version of iPhoto
I hope that helps - I am not clear on your question
If I open iPhoto, select the EHD as the source, doesn't that create the situation where I will always have to use the EHD as the source?
I want to transfer the data to the MBA as described above. Any suggestions how?
When you open iPhoto and hold down the option key, you tell iPhoto where your iPhoto Library is and it uses that Library and the photos contained within it. Next time you open iPhoto, it will go back to the last iPhoto Library you used with it. If you open iPhoto again with the option key held down, you can switch to another iPhoto Library. You don't always have to use the EHD as the source just because you used it once. You can specify another location for your iPhoto Library.
To access the photos on the MBA from the EHD, simply connect the EHD via USB to the MBA and hold down the option key when starting iPhoto on the MBA. Then tell iPhoto to use the iPhoto Library on the EHD. Or simply copy (drag) the iPhoto Library from the EHD onto the MBA's internal drive. Then start iPhoto with the option key held down and point to the iPhoto Library on the internal drive (which will be faster since that is a solid state drive).
Open two windows on your screen on the MBA. One window should show the EHD with the iPhoto Library file visible. The second window should be the Pictures folder on your MBA. Since the EHD and the MBA are two separate hard drives, when you drag/drop the file from the EHD to the MBA drive, it will COPY it. So drag/drop from the EHD to that Pictures folder in your acocunt on the MBA. Then on the MBA, start iPhoto. If it asks where the iPhoto Library is, point it to that just copied file now inside your MBA Pictures folder. If it opens some other iPhoto Library file, close iPhoto and open it again holding down the option key and direct it to that MBA Pictures folder iPhoto Library just copied from the EHD.
With iPhoto, you can change the iPhoto Library you are using for a session by starting iPhoto and holding down the option key. Some people have multiple Libraries and change between them this way, keeping them in that Pictures folder, in some other folder, or on a variety of internal or external drives.
Thanks Steve. Your response was spot on. The only detail lacking was the "two windows" could have been said "two finder windows". I followed the advice exactly and it worked like a charm. In fact, it makes it easy for me to consider other options by making multiple bakups of select images. Now that I see how it works, I can fiddle with the process to meet my needs.
Now I need to see how this may effect my use of Aperture......not wanting to stray too far from the original thread.
Well, I'm not an Aperture user, but my understanding is that with the most recent version of iPhoto, both iPhoto and Aperture use the same iPhoto Library for their libraries. So in fact, it should be possible to use either program, make updates to the iPhoto library, and then use the other program. (Apple's web site touts this capability, in fact.) So I think that everything you're doing with the iPhoto Library is relevant for Aperture equally well.