Using the digital camera requires us to understand a few technical concepts before we can use it fully well. These are also science and some of these concepts have to do with using light and the camera to capture the best possible pictures.
While not every camera is manufactured with the highest possible capabilities and that is very much so because not everyone wants to take excellent pictures. Some of us take to photography very seriously and some are amateurs while others want to have fun with their camera phones.
But if you are planning to buy a digital camera, first make an attempt to learn what ISO is. It is easy to learn. Digital cameras have a sensor. ISO measures the sensitivity of the sensor to light. Light in our environment changes. The ISO should be set accordingly to allow us capture a picture in its best.
ISO of a digital camera should be higher. For darker situations, sports, indoor shots, a camera with a higher ISO is preferred. When setting the ISO of your camera, take into account the amount of light in the scene. On a broad daylight scene, ISO can be set to low.
The ISO setting if high the camera would take a faster shot. However, it is not necessary that a higher ISO setting is to be used for every shot.
When the ISO setting is high, the picture turns out grainy. It may not be evident when seen through the
LCD screen of the camera but when you transfer the photo to the computer, the noise will become obvious.
Hence, simply increasing the ISO is not the solution. One can also lower the aperture F-stop number. If the camera is still not shooting fast enough, increase the ISO number.
To answer the question of how to set it right for different situations, it should be a mix of speed and photo quality. Measure the light around you and set the lowest possible ISO that allows you to shoot without blurring the subject.
For a daylight scene with ample sunlight, set your ISO to 100. For capturing objects set in shade but in a sunny weather, start with 400. Take into account the shutter speed. It should be faster than the mm length of the lens. To understand better let us take an example. If the camera lens is 100mm then the shutter speed should be at least 1/100th of a second.
If the shutter speed is slower than the length of your lens, then increase the ISO setting and try again. This way you can capture animals or people standing under a tree on a sunny day. For rainy days or days when the weather is overcast, set the ISO to 400.
But check the aperture F-stop also. The final setting of the two will decide the quality of the picture and the settings will change depending on the scenario.