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Good choice on the camera. I play with that thing alot at work, though I'll never afford it. I will say one thing about Nikon's cameras though: I think they take fantastic pictures, their build quality is good and their lenses are superb - but their menus, buttons and physical controls are very unintuitive, and not well thought out or layed out in general.
Whenever I hold a Nikon, I have to stop to think about where the button I'm looking for is. (Maybe it'll be buried in a menu, maybe not. I STILL don't know how to activate continuous shooting on the thing. A customer and I looked for it for a good while, and found nothing). Whereas the Sony Alpha 700 for example, is quite intuitive and the Pentax k10 trumps them all in terms of mindlessly-easy and intuitive controls. I just wish they'd overhaul the standard Nikon layout. (It's still a wonderful machine though! hehe)
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But about your shots. They're a good start. With a bit of tweaking, they could be a great start. One thing I myself am often guilty of is not thinking before pressing the shutter(Seriously, I do it way too much. I just get so excited sometimes "Ooh, something pretty! Snap!" hehe). I'm only recently starting to "get" the concepts of compositions and depth and such. Those two things are really what all three of these shots need.
Like in the first photo, there's no clear object that is the subject of the shot. All I see are things in front of the camera, not a photograph-of-something, you know what I mean? I also don't know if the off-white-balance was intentional, but it works here.
The second photo needs more. It may be personal taste, but I would never, NEVER use your undiffused onboard flash to light your subject directly. I've never seen it look good from any camera, ever. Plus the flash upped the light on the subject, which made the exposure black out the background, which when combined with the head-on lighting, really flattens the image.
Try getting closer to the gnome and lower to its eye level, then either significantly reduce your flash's power or bounce it up(with your hand or a piece of paper) so that it indirectly lights the gnome, instead of head-on.
The rest is up to you, but I'd personally keep the aperture as wide as possible, for some nice bokeh, texture and depth in the background. I guess a VR lens would be good for you there, so you could slow the shutter down some.
The third shot is okay. But was it taken through a window? Or was it kind of hazy out? It lacks some punch. And again, the shot might have been a bit more interesting if more of the background windows OR more of the track's support columns were in the picture. It's kind of uninteresting having it right in the middle. This shot might also look good in portrait, I dunno, I'd have to be there to be sure.
Sorry for all that, maybe you didn't want critiques, maybe you did.
