Aperture
Aperture is a measure of how open or closed the lens’ iris is. A wider aperture means more light will be let in by the lens, simply because the opening is larger. A narrower aperture allows less light to reach the sensor. You might wonder why we would ever want less light to reach the sensor. The answer the majority of the time is that we want a larger depth of field. Depth of field is a byproduct of aperture. Narrower apertures give a greater depth of field, allowing more of a scene to be in focus. Wider apertures create a narrow depth of field, which can help isolate a subject and is one of the greatest composition tools at your disposal (think portraiture).
Shutter Speed
Shutter Speed is the only thing between the light that has passed through the Aperture and the image sensor is a shutter. Shutter speed is a powerful tool for freezing or exaggerating the appearance of motion. Shutter speed is a setting on your camera which controls the length of time the shutter is open. Shutter speeds can go from very small fractions of a second, to several seconds long on most cameras. On a bright day when there is a lot of light, if you allow the shutter to be open for too long then too much light will get to the sensor. When this happens you end up with pictures that are very pale and almost all white. This is known as being called over Exposed.
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ISO
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ISO measures the sesitivity of the image sensor. The lower the number the less sensitive your camera is to light. Higher ISO pictures are often considered noisy, in the sense that they become grainy or contain discoloration when used in well lit areas. Therefore they are generally used in darker environments.
The photo effects you want to achieve with the aperture and shutter speed will impact the amount of light reaching the sensor, so you use the ISO to adjust its sensitivity and get a good exposure |