Once you get the hang of controlling the size of your aperture and how long it stays open, there are two more settings to consider.

White Balance describes the color temperature that your camera uses.  A “warmer” color temperature will shift the color hues away from blue and toward oranges, whilst a “cooler” color temperature will shift the color hues away from oranges towards blues.  In general the “auto” setting on your camera is sufficient.  There are some situations, however, when it’s not.

When you are shooting in a low-light or high-shadow situation such as a forest floor, the white balance will tend to skew towards the cooler temps, leading to a blue cast to your shots.  This sometimes happens when shooting snowy scenes as well.  Setting the camera’s white balance to a warmer temperature will help.  When shooting under artificial lights, especially florescent and industrial lighting, the white balance will tend to skew towards the warmer temps, leading to an orange cast to your shots.  Setting the camera’s white balance to a cooler temperature will help.  Most cameras label their white balance settings for the scenes they are meant for: sunset, daylight, shade, flash, etc. If you want to take complete control you can pick up a “18% Grey Card”, which is a piece of cardboard colored 18% grey, and then shoot it under the light your subject will be under.  You can then tell your camera to use that shot to calibrate white balance.  Exactly how you tell your camera to use this custom white balance varies by camera, but your  manual should be fairly clear.  If you don’t have an 18% Grey Card then you can find a patch of white and use that, remembering to compensate your exposure.

ISO Number describes how sensitive your sensor is.  A higher ISO number means a more sensitive sensor.  A more sensitive sensor will record an image more quickly than a less sensitive sensor.  So, in low-light situations where you can’t make your shutter speed any slower and you can’t make your aperture any larger, you can increase the sensitivity of your sensor to get the shot.  However, a more sensitive sensor is also more “noisy”.  So the resulting image can appear grainy or speckly.  This problem becomes worse if you enalarge the picture.