JPEG degradation

I'm aware that every time I open a JPEG file, edit it (ie rotation, contrast, color temp, etc), and then close the file that when the file is closed it goes through a decompression process resulting in some loss of image quality. My question is, does this decompression and loss of image quality happen every time the file is opened only for viewing (say a slide show)?
Here is the main reason I have this question. As many of you have disappointingly learned, the Nikon D50 does not produce RAW files that iPhoto can read. Since I didn't really want to install and learn the Nikon software, I thought I'd just shot in JPEG Large/Fine and be satisfied with the image quality. But if every time I view my photos or show a slide show there is going to be some image degradation then I'll have to have a way to import Nikon D50 RAW files onto my computer.
Thanks to anyone for any information.

Scott,
Nope. You lose nothing when you view an image. Don't think you will lose anything when you rotate an image either.
Technically it goes through a recompression process.
Also, iPhoto does a clever trick where it "remembers" the compression it used. So you edit a JPEG once and it shrinks the file. You can edit it as many times as you want after that and it won't compress or degrade the image any more. This is argueable though. Test it for yourself. Dupe an image and edit it ten times with minor adjustments (click the exposure icon to move it one pecent or something.) You'll see the file size shrinks the first time, but doesn't thereafter. Press the "2" key to enlarge both images to max size and compare. Most people can't really see a difference.
RAW is good if the exposure of your images is off. It's main strength is that you can re-expose the image if you have a raw file. Then iPhoto makes a JPEG of it for editing anyway. So if your camera is producing good JPEGs, RAW is not really as great a thing as it's made out to be. Many pros shoot JPEG and feel that fooling with RAW is just another unnecessary step added to the process and takes up a lot of card memory they could be using for more images.
Kevin

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