Depth of field is the distance wherein objects are in focus. If you want to decrease the DOF, you can do that by using a large aperture, moving closer to the subject, or by using a long focal length. You can also increase the DOF by using a small aperture, moving away from our subject, or using a wide-angle lens. A change in focal length allows you to come closer to the subject or to move away from it and has therefore an indirect effect on perspective. A wide-angle lens has greater DOF than a telephoto lens. Generally we have three ways to control DOF in our pictures:
1. By lens aperture or the size of the opening that allows light to go through the lens. A large lens aperture gives a shallow DOF, and a small lens aperture gives great DOF. In most advanced consumer digital cameras you will be able to directly control the lens aperture.
2. By distance from subject or focus on subject. To obtain greater DOF, you just need to step away from the subject. To decrease DOF you just need to move in closer to the subject, because when you focus on a subject close to the camera, the DOF is less than when you focus on the subject farther away from the camera.
3. By focal length or the amount of the scene your camera can see left and right. The focal length of a lens establishes the field of view of the camera. By adjusting the focal length on your camera, you affect the zoom.
The amount of scene that the camera can see in inversely proportional to the focal length of the lens. The larger the focal length, the higher the amount of zoom which yield a smaller scene view. The smaller the focal length, the more scene will be visible. Some digital cameras suffer from barrel distortion at the wide angle end and from pincushion distortion at the tele end of their zoom ranges.
White balance is the concept of color temperature. It is very important to know that different light sources emit light at different colour temperatures. Color temperature is a way of measuring the quality of a light source. It is based on the ratio of the amount of blue light to the amount of red light, and the green light is ignored. The unit for measuring this ratio is in degree Kelvin (K). A light with higher color temperature (or larger Kelvin value) shifts light toward the blue and a light with lower color temperature (or smaller Kelvin value) shifts light toward the red. Read more...
Usually digital cameras have built-in sensors to measure the current color temperature and use an algorithm to process the image so that the final result may be close to what we see (with our eyes, of course). Most advanced digital cameras provide the feature to manually set the white balance by using preset WB settings such as, Tungsten, Fluorescent, Cloudy, Sunny, etc. Using preset WB can improve on a picture, especially under indoors lighting. With some cameras when the in-camera algorithm is not able to set the color temperature correctly or when some creative and special effects are needed, you can instruct the camera to use a particular color temperature to fulfill specific need. Just follow the manufacturer instruction manual if you need to do that.
NOTE: Don't forget to reset this white balance setting when you head back outdoors into natural light, or you may end up with some strange, out of this world, colours.