A Brief Camera Primer
I'm not sure where to begin, so I'll start...here. Well, what are you interested in shooting? If you know that answer, then you'll know what lens to surely pack if you're an SLR user. Shorter focal lengths, or wide angle lenses, will capture just that - a wide field of view. Longer focal lengths, or telephoto lenses, will capture a narrower field of view, as if viewing through a telescope. Choose according to what you want to photograph.
Unless depth of field (the distance in front of and behind your main subject that is in apparent focus) is of utter importance, I almost always use shutter priority (Tv on the mode dial of most cameras). In doing so, I get to choose how much motion I want to incorporate into the composition. Eliminating or minimizing motion blur from moving subjects with a fast shutter speed lets you record a split second in history, whereas including some motion blur with a slower shutter speed can invoke a completely different emotion in a photograph.
Once I've chosen a shutter speed, or time value (that's what Tv stands for), I set my best estimate for exposure compensation (based on the type of metering I've chosen), set the ISO to auto, and set the white balance to best match the main light source illuminating what I am photographing. The aperture is chosen automatically in this mode.
You might be wondering about camera shake. Make sure image stabilization is turned on, whether it be on the lens, or the camera body. There is a guideline for what the shutter speed should be to avoid camera shake, and it is based on the focal length: 1 / focal length. For example, if using a focal length of 55mm, choose 1/60 or faster. At focal length of 200mm, choose 1/200 or faster. Remember, these are just guidelines. Experiment with them! Keep your arms close to your body when holding the camera, and/or brace yourself on something stable, such as a building, or a bench. The weight of the camera/lens should rest in your left hand to allow for a stable and jitterless press of the shutter button. Shooting in different lighting conditions will give you a feel for the shutter speeds required.
This primer is not intended to help you get around your camera. That is your job. You should become familiar with your menus and buttons so that you can make adjustments without having to continually remove your eyes from the viewfinder - know how many clicks on the main dial (if you're using a point-and-shoot, you might have one) it takes to adjust one full stop.
I am only here to get you out of the ever-so-comfy "green" mode, or fully-automatic mode. Camera brains are becoming smarter, but there are certainly situations where you will need to take over in order to capture what you want to see. This is especially important when there is only one chance for the shot. After break time, I will attempt to clear up the fogginess of all the different letters you see beyond the green square on your mode dial. Yes, the mode dial is different than the main dial. Typically, the main dial adjusts camera settings, where the mode dial is used to switch...modes (Av, Tv, B, M, or scene modes).
Aperture, Shutter Speed, and ISO
As explained above, the aperture is the size of the opening that allows light to hit the sensor (used to be film) of the camera. Smaller f-numbers increase the size of the aperture, where larger f-numbers decrease it. Aperture controls the depth of field - the area in front of, and behind the main subject that is within the area of sharp focus. Sorry, no pictures to illustrate, but if you're wondering how people get the blurry background in a portrait, they most likely shot with a large aperture...yes, the smaller f-number. If you want more to appear in focus, choose the larger f-number. So, to recap, aperture controls incoming light, and depth of field. When shooting in aperture priority, the camera automatically chooses a shutter speed, which is based on how you meter the scene...huh? Just wait.
Ah, shutter speed - the all-powerful exposure setting. This parameter controls incoming light as well, and the amount of motion you want to see. How do photographers make city streets looks busy with light streaks - a long shutter speed...oh, and a tripod. When shooting in shutter speed priority, the camera automatically chooses an aperture, which is, again, based on how you meter the scene...huh? Waaait!
Oooh, ISO. I'm not sure how to explain this one. Oh, I know, it controls how sensitive the camera sensor is to incoming light. Clear as Mountain Dew? I just thought of this real-life example. Take your skin, for instance. When it's not sunburned, you can feel someone touch your skin, and everything's great and normal - this is like your camera at a low ISO, such as 100. When it is sunburned, and it feels as if your skin's going to rip off, when someone touches it (the exact same way as before), it REALLY hurts. This is like your camera using a high ISO speed, such as 1600 - where it will not take much incoming light to create an image on the sensor. Along with sunburn pain, high ISO speeds bring digital noise into the photo (used to be film graininess). The rule of thumb is, lower ISO is better, but if you can't get the shot any other way at that very moment, use the higher ISO to get the shot.
Break Time, and Metering
Oh yeah, I never discussed metering...wait a minute, it's break time. Ah, back to business. Metering is the camera's way to evaluate what settings will be required for a properly exposed image. When I say properly exposed, I mean that the outcome will be the camera's best guess at recording what we see with our eyes. However, the camera sensor's dynamic range (the spectrum of shadows and highlights in any given scene) is outmatched by the abilities of our God-given eyes. So, we have to help the camera determine what's important in the scene we want to capture.
When you choose a metering mode, you're telling the camera how much of your scene to evaluate. For example, evaluative metering covers a much larger area in contrast to spot metering. It is a way for you to tell the camera where to direct its attention so that its brain can calculate proper settings.
It is important to know how to interpret the ±2 or ±3 that you see on your LCD or viewfinder. The "0" that lies in the center of that range of numbers refers to 18% gray - the tone that lies in the center between black and white. Some real-life objects that closely represent that tone are a clear north sky and grass as seen in midday. Read up on Ansel Adams' Zone System. You will gain much intuition on properly exposing your shot right off the bat.
So I've read, "studies" have shown that our eyes tend to look at certain places in the frame first, before looking everywhere else. Don't be afraid to keep your main subject off-center. It actually adds more umph to the photo. There's this thing called the Rule of Thirds yada yada, but it's an excellent guideline to help compose your photo to be more aesthetically pleasing. Yes, I said guideline. There are exceptions where it may not produce the best result, in which case you'd make something work in order to produce a striking photo. Oh, the Rule of Thirds is where you divide (vertically and horizontally) the frame into thirds, and place your subject of interest at the intersection of those lines, or along those lines. Your camera might even have a mode to superimpose a grid onto your screen to help you compose shots. Does everything have to be off-center? Of course not. It may be excellent placement for elements containing symmetry, and could make for an interesting photo with the right crop job (trimming away the edges of the photo, leaving only what is necessary to convey to your audience, that sense of Eureka at the moment of capture).
Break Time, White Balance, and The Meaning of Life
I've said too much. Go take photographs. Challenge yourself in different lighting conditions, and even mixed lighting conditions. Oh yes, white balance. For the most part, choose the appropriate light source on your camera that matches the environment you're shooting in, so that colors appear as accurately as you see them with your eyes. If you're looking at a hot scene with some cool shades on, your photo will appear blue (or, cool). If you're looking at a cool scene with some hot shades on, your photo will appear red (or, warm). What? Okay, let me say this again. If you're looking at a 5500K scene with some 3200K shades on, your photo will appear cool (or, blue). If you're looking at a 3200K scene with some 7000K shades on, your photo will appear warm (or, red). It's okay, it's just color temperature. Yes, color has a temperature. No, not a fever. Just go shoot. Post processing can fix EVERYTHING. REALLY?! NO, NOT really. Save a ton of time up front and become familiar with your gear, and get the shot right the first time. Of course, there will still be a little post processing. I mean, you're trying to get a man-made sensor to see just like your eyes. It ain't happenin', but you can get pretty snug to reality.
Not that I'm biased or anything, but there is a lot of freedom when it comes to night photography, when your camera can soak in a scene for thirty seconds...or two and a half hours. Night is more colorful than you think. Go! Embark on your photographic journey. You can see the world from your viewfinder through your lens, and others will see you from your lens, through your eyes.