why does iPhoto make each photo slightly blurry when I look at it?

I am looking for a solution for this too. When I open the same photos in Lightroom they are crisp. So it is for sure an iPhoto problem. Not a photo issue.

Is it blurry when you double click on it to view in the larger size? It might be a rendering issue at sizes less than 100% but doesn't affect everyone. When I hade it I found that resizing the photo with the slider every so slightly it will snap into sharp focus. Report the issue to Apple via http://www.apple.com/feedback/iphoto.html.

OT

Apple has not fixed this problem inspite of all our ranting and waving... But I did find one solution (be as it may) -After you have edited your picture, click on "Edit" on the lower right and the image will be clear again.

Unfortunately you have to go back and forth as you edit the pictures (clicking on edit, and then clicking on edit again to see the finished product). At least you'll be able to see it on the bigger editing screen.

(Come on APPLE, there needs to be an easier fix!)

There was a post on this earlier in the year. It seems to affect only some Macs with some graphic cards, and one person found that simply forcing the screen to redraw will do the job. (Which is essentially what you're doing there). Her method, iirc, was to click on the boder between the left and right hand panes and nudge left or right a fraction. Another fixed it my maximising the window by clicking on the green button.

Just so everyone knows, it does work to view it not in editing mode. Like Rivoz said, if you're editing the photo and it looks blurry, click edit on the bottom right so it's just in viewing mode without the editing panel and it looks normal again. Easiest temporary fix.

You do realize that you're posting to a 2 year old topic and iPhoto has gone thru several updates between then and now, right?