From: pixel_a_ted on
Posted this elsewhere with not much luck...

I notice that if I am in Finder and double-click on an image file
(jpg), the resultant image is slightly sharper on my monitor than the
same image after importing it to iPhoto and viewing it there after
double-clicking on the thumbnail. The image size on the screen is the
same in both cases and the image is being viewed at 100%.

Here's another observation - if I export a photo from iPhoto using
Maximum Quality and Full Size then it appears as sharp as the
corresponding (original) photo in Finder when both are viewed with
Preview.

There's something about the way the photos are being displayed in
iPhoto - some degradation of sharpness compared to the image you get
outside of iPhoto using Preview.

Any ideas?

Thanks.