Aperture Settings for Portraits

A few weeks ago I came across an article about aperture settings for portrait photography. It said a good rule to follow is to set your aperture according to the number of people in a shot (2=2.8, 4=4.0). This is something I had been wondering about... I hate taking a family photo where some people turn out blurry and others are in focus. I decided to try this theory out for myself and these are my results:

I didn't see a huge difference with 2 people in the shot. I think I should have shot the second picture at f/2.8 and I think it would have worked much better!

The theory worked better with these photos. They all look pretty clear in the second photograph.

I saw the biggest difference with these photos. Everyone in the bottom photo is much clearer than in the top. However, I like the background effect in the top photo much better...I guess it's more important to have everyone in focus than to have the background blurry.

All in all, I think this theory is a pretty good rule to follow, or at least somewhere to begin when taking portraits.