This is the first in a series of articles I plan to write on photography. While I don't claim to be an expert by any stretch of the imagination, I thought that I could use some of my photos to illustrate some concepts.
With a zoom lens you have a range of focal lengths available to you. This can change your shot from being a wide shot to a telephoto shot, all without moving your feet. Of course, this will depend on the range of your zoom lens but you will be offered at least somewhat of a decision between wider or tighter/narrower.
It's worth noting that while you can change how the shot is framed, zooming in or out with your lens will not change the perspective or angle of view. This can be both good and bad. A good thing about this is that it can allow you to avoid distracting elements and then you can play with the zoom until you get the framing you like. The bad side to this is that a zoom lens can make you lazy and you can get into the habit of not moving around to find other perspectives to take the picture from. The key is to still be thinking about different perspectives and try moving around. Once you've found an interesting perspective, then you can play with the zoom until you've found something that really works.
I've selected 2 of my photos to illustrate how much of a difference the zooming can make. Both of the pictures were taken at the same spot without moving in between. I was using a 28-105mm lens (a very versatile range) so the difference between the shots is quite dramatic. If your zoom lens doesn't have as much range then the difference will be less extreme.
This image was taken with the zoom lens on a wide setting (probably 28mm but I didn't record it). It gives a nice impression of the narrow streets of Stockholm. The walls really draw your eye into the photo towards the yellowish-orange building at the end (which was what originally caught my eye). However, the building is extremely small in the shot and so I feel that the photo isn't all that successful. I feel that too much of the shot is taken up with the walls and the street, which aren't all that interesting.
On the other end of the spectrum, this image was taken on a long setting (probably 105mm but again, I don't have it recorded). I've also switched to a vertical shot which makes the shot even narrower (but it gives the shot a very nice verticality). In this shot the building at the end of the street is much bigger and your eye is still led towards it because of the walls converging towards it. While neither image is among my favorites, I still consider this image to be far more successful. The main subject is now clearly the building at the end of the street. In the first image, your eye is still drawn to the building at the end of the street but it's really too small to be the main focus of the picture.
I hope that this has helped show how just a simple change on your zoom can completely alter your shot. You can use a zoom to either give a wide expanse, or pull tightly into one particular point of interest. I've been taking a photo course at my community college and my instructor mentioned a couple of weeks ago (as of the writing of this) that it's best to start with your zoom as tight as it gets. Then, slowly zoom out until you get the framing you like. I think this is a good rule of thumb to use. If you apply this then you should be able to get a nice tight framing of your subject. If you start on the wide end though, you can end up just taking the shot right away (because all of your subject will be in the shot), but you can end up with an image where the subject is very small and not really the centre of focus. When you start zoomed all the way in though, you may end up not having all of the subject in the shot (to begin with), but you can then pull out until you do have everything in the shot. Even after you've done this though, you may want to play around with the zoom. You never know, something else might catch your eye and give you another image. It's also just a handy exercise to see how much of a difference in the image the zooming makes.