To understand photography it is necessary to understand three factors of great importance that will be shown below and a correct equation based on it will depend much of the sharpness, depth of field, light and quality in the image of your photographs, as well Taking note will be very helpful.
DIAPHRAGM AND DEPTH.
The greater the aperture of the diaphragm, the lower the depth of field and the depth of field is the distance in front and behind the focused point that appears sharply. To control the quality that the camera captures, the objective has levels of opening, which close or open to the double in each step with a mechanism that imitates the movement of the ires of an animal eye. The openings are with the letter F, the higher the numerical value, the smaller the amount of light and also the depth of the field.
OBTURATION AND MOVEMENT.
It refers to the amount of time that light passes through the open diaphragm to project in the photosensitive the image that has been framed, that is, the time that each shot lasts. It depends on whether your objects are captured in motion with a swept effect or "freeze" them completely.
ISO
He was referring to the sensitivity of the photosensitive film, which was a scale determined by the International Organization for Standardization and although digital photography currently works in another way, it is still called the "reaction" that the camera has based on a quantity of light available. The higher the ISO, the lower the amount of light needed.