So far I used borrowed analog SLRs + iPhoto. I now got a Nikon D40x, always shooting RAW, and iPhoto doesn't work for some pictures (for whatever reasons). I downloaded the Aperture 2 trial version and worked on a picture. The results can be seen here: http://gallery.mac.com/stahlchristian#100121&bgcolor=black&view=mosaic&sel=0 1. Aperture 2 correction by me, a layman; 2. Aperture 2 incl. "dodge and burn" (the top of the prospect + the two angels at the top left and right); 3. iPhoto correction; 4. Original
Sorry, I forgot my question: Is the iPhoto/Aperture 2 difference really so big at first sight? (That's what I need pictures for the most, as an eye-catcher). How big is it? It was 5 min vs. 2 hours for me, but that only results in me being unable to name the difference. Now I know the motive and a good "eye" - that's No. 1 for an "eye-catcher", but that would be another question in another forum (hints welcome, though).
I can't answer your question exactly, but true raw processors like Adobe Camera Raw, Aperture, Lightroom, and a bunch of others apply their parameters while the image is still in its raw form. iPhoto and others render the raw (at least iPhoto's rendering is 16-bits), and then operate on the rendered image. Not nearly as powerful. (I'm not talking about iPhoto passing the raw to an external program, I'm talking about iPhoto processing it with its internal editor.) This is at most a partial answer to your question.