Sometimes when you take pictures with your digital camera, you turn your camera sideways to get a better vertical shot. But then when you import your photos into iPhoto, the photo is horizontal. And you want it displayed vertical. Like the picture of the darling baby in the photo below.
But then you notice that the Rotate button in iPhoto rotates the picture the opposite way than what you want. One way to solve that problem is to hold down the Option key on your keyboard. When you do this, you notice that the Rotate button switches the arrow to rotate in the opposite direction. You can then click on the Rotate button to rotate the picture in the desired direction.
Watch the little movie below to see how the arrow changes. (You won’t be able to see me holding down the Option key on my keyboard but know that when you see the arrow change directions on the screen that is what my finger just did.)
You might find that the great majority of the time you need to rotate in the opposite direction than what the Rotation arrow is. If so, you can make a change in the preferences. In the text menu at the top of the iPhoto screen, click on iPhoto and drag down to Prefercnces. In the Preferences window, click on the General tab. Then, click the Rotate radio button that you want. See the picture below.