Thanks Pete, for the very precise explanation. Just what I was looking for.
I understand the Focus issue. The DOF issue is new to me and I get it. But why can you get away with lower shutter speed? I mean: What's on the screen/view finder is only a representation of what's going on on the sensor, isn't it? So how is the shutter speed affected by the way you look at it?
P.S.: You're kidding about the photo taken by your son, eh? He didn't reallytake THAT photo at the age of 9...?!
Hi Gabriel my Grand Parents were German and I spoke German fluently when I was younger(but not anymore), I grew up in Denmark just a few KM from Germany
The shutter speed is affected by how steady you are holding the camera, so when your are looking at the screen your camera will move around more than if your are holding the camera against your eye and closer to your body, this can allow a lower shutter speed and a better aim
My son Mark has the use of my backup camera D80 and yes he actually took that picture. His toy Motorcycle was placed inside a photo tent on a black surface/back ground, flash on the out side fired by wireless remote, camera in M mode, but AF on for the 16-85 zoom lens. I was trying to show him what happens when you turn power up and down on the flash(vivitar 285) or move it closer or away from the side of the tent. He knows how to shoot, is slowly understanding what happens when you adjust aperture. Anyway he took a few hundred pictures of different toys, this is the one that I liked the best by far. Yes digital camera are great in allowing you take take lots of pictures and use your display to fine tune your picture
Using the flash off camera is also great for portrait pictures, the flash just fired straight in their face is not really the best way for a great picture. The D90 can control the SB 600 off camera, The 50mm F1.8 is a very Sharp lens and great for portrait, you might find the 18-200 lacking in that quality, you could also purchase the D90(D5000 if you have to) with this lens combo (18-55 VR and 55-200 VR) which are BTW very sharp, check reviews of them
I do use my liveview to take pictures, the leaf/bridge in the Photo-a-day was taken in liveview and it would have been easier if my screen on my D300 could Vari-angle like on the D5000 but I do without
To end this the 18-200 lens is not the best choice, it sounds like you want to get good at taking portraits, a flash could be of help to you.
So here is a starting kit idea:
D90/D5000 18-55 VR, 55-200 VR (this are often sold in kit/package price) 50 F1.8 (MF on D5000 and a SB 600 flash (D5000 can not control flash remotely by it self)
Whatever you get have fun with it, visit NR in the future and don't forget to submit a few pictures to the Photo-a-day