Photography is literally painting with light and controlling light is the most important thing that you need to know how to do in photography. Outdoor photography is very different from shooting indoors mainly because you can't control your primary light source, the sun. The sun is much more harsh than indoor light, and thus it's best to photograph outside when the sun is either rising or setting. This is because the light travels at an angle and passes through more atmosphere before it reaches you. The dynamic range of light between the darkest shadows to the lightest highlights are therefore less than when the sun is pounding directly above you at midday. Also when the sun is at an angle, shadows are such that things tend to seem more three dimensional.

Cameras cannot capture the full dynamic range of light during the midday sun so either your highlights will be blown out or your shadows will have no detail and the contrast is too harsh. Cloudy days help diffuse the light and will lend to softer, but flatter, images. Combining a cloudy day with an off- camera diffused flash can work really well for outdoor portraits. You'll want to experiment with different light placements to get the effect you're looking for, but generally a light source that is higher than the subject is a good place to start because it's the same angle the sun would travel to get to your subject and thus it looks more natural. You can put a sock or some other translucent object around a speed light to get a diffused light source that is relatively cheap and mobile.

Shooting at dawn and dusk comes at a price though. The overall light is less and therefore, you need to compensate for that to get a good exposure. There are 5 different ways gather more light for your picture.

You can use a larger aperture up to the maximum that your lens allows. This is represented by the f number. For those mathematically inclined, you can think of the f number as a fraction, and therefore f/2.8 (think of it as 1/2.8) is larger than f/5.6 (which would be 1/5.6). Changing the aperture has an interesting effect typically referred to as bokeh, which means the blurry part of a photo that's not in focus. The larger the aperture, the less of the picture will be in focus. This is desirable for wildlife, portraits, macros, etc, but tends to be less desirable for landscapes.

You can slow down the shutter speed. If you're shooting an inanimate object such as a mountain or landscape, it's perfectly fine to have a long exposure of 1-2 seconds or more if you need it. If it's windy, your trees and grass are going to be blurred though. If you're shooting water such as a stream or waterfall, usually you actually want the water to be blurred. If you're shooting a portrait, the person is really going to be angry if you make them sit there still for 3 seconds for each shot.

The camera has an ISO setting, which mimics 35mm film speeds. The higher the number, the more sensitive to light the camera becomes, and the more grainy the picture ends up. Therefore, the higher the number, the less light is needed to expose your picture properly. Some higher end cameras have the ability to reduce the grain and noise so you can shoot at high ISO values without losing too much picture quality. It's typical for a camera to be able to go to ISO 1600 and many newer cameras will go to ISO 3200. Some pro cameras will even go to ISO 6400, which is excellent for low light situations.

You can also use exposure compensation with varying degrees of success. My suggestion here would be to only use this if everything else is maxed out.

The last technique to simulate more light for your photo is to use HDR technology.  HDR stands for high-dynamic range. Essentially, what you do is take 3 or more photos of the same subject using a tripod to keep each image as close as possible to each other. One photo is slightly under exposed, one photo is normal, and the third photo is over exposed.  Then, using software, these photos are combined into 1 thus creating a better range of color in the image.

Typical outdoor photography during the day needs an ISO of 400 or less and increase that the closer you are to dawn or dusk.

Using a combination of aperture, shutter speed, and ISO, you can expose a picture properly in most situations. Problems come into play when you're photographing a fast moving object in low light because you might not be able to have a fast enough shutter speed to keep the subject sharp and have enough light. If that's the case, you'll need a lens that has a larger maximum aperture or a camera that has a higher maximum ISO rating, which both tend to be pretty expensive. When shooting fast moving objects, there's also the desire to zoom in on that object as close as possible, which means you'll need a telephoto lens. Combine a good telephoto lens with a large aperture, and your price just jumped into the thousands of dollars; therefore, it's a good idea to learn what photographs you can get with the equipment that you have unless you can afford expensive camera equipment.