The first photo worked fine. Keep in mind that using a larger aperture (F 4.5 and wider-meaning smaller numbers) will separate your subject from the background.
In the second photo the varying distances the person are from the camera to their position will shift or change the amount of light that falls on them. In other words, the person farthest back from the camera gets the least light, while the person closest to the camera, and thus the flash unit receives the most light. The amount of light received by each person will cause a difference in facial color tone of each person as is seen in the resulting photo. The logical question is how do you overcome this problem when photographing a group of people? If you had a powerful external flash you could use bounce flash and get very even lighting and better facial color tones throughout the group.
But the problem is that the Nikon P-90 does not have a hot shoe, does that rule out an external flash? No, it does not. A slave flash with a moveable flash head could provide the help you need. A slave flash is fired optically, meaning that when the P-90's built-in flash fires, the slave flash fires as well. The two flashes are in synchronization due the speed of light which is very, very, fast.
In the attached photo you will see the Canon SX-10 and its external flash on the left and the Kodak Z-980 camera with its external flash. Notice that the two flash heads are adjusted to a different tilt angle. When you use external flash you need more flash power because you are bouncing it off a white ceiling.
A flash diffuser such as Gary has suggested will work only on close up subjects, it will not work with a group.
Last edited by mtclimber; Aug 20, 2009 at 12:53 PM.
Reason: to add the photo