I recently took the next step in my growth as a photographer: buying a 50 mm lens. From what I've learned on photography forums and blogs on the internet, a 50 mm prime lens should be in every professional photographer's camera bag. Unlike a zoom lens, a prime lens has only one focal length, and thus its optics can be optimized for that specific length. As a beginner, a prime lens is good practice because it forces you, the photographer, to move a lot more to frame a shot, since you can't just be lazy and zoom in or out.
The other thing that my 50 mm prime lens allows me to do is to add close-up lenses to take photographs of very small things. Below are my first attempts, within minutes of unboxing my close-up lenses.
Lens cap. The obvious choice of object lying around to take a close-up shot of.
Index finger on desk.
My fingerprint. Please don't steal my identity.
You can see one of the cuts I sustained while breaking into my own house.
Smallest possible Neocube. Each ball is about a half centimeter in diameter.
Quarter dollar. Here, and in the lens cap shot, you can see the trade-off with macro photography: you get a very, very, very thin depth of field. Consequently, this is why artificially reducing the depth of field (tilt shifting) can make the subjects of large photographs appear small.
Look for more close-up photography here in the future. I'm just getting started...