Читать книгу Collins Complete Photography Projects - John Garrett - Страница 26

Before you start shooting pictures with your camera you must select the ISO setting, either from a button on the camera body or via the menu.

The ISO (International Standards Organization) index is a system for calibrating the sensitivity to light of film emulsions and digital sensors; the higher the ISO number, the greater the sensitivity. On most cameras the ISO settings go from 100 to approximately 3,200, though the latest digital sensors allow settings of up to ISO 25,000.

The lower the ISO number, the finer the quality of the image, whether film or digital. As the ISO number rises so does the amount of noise in a digital image and grain in a film negative, breaking up the image and reducing sharpness and detail. Noise reduction can be turned on when shooting at higher ISOs, but it tends to soften the image somewhat. It has no benefit at low ISOs.

Grain and noise are not necessarily a bad thing – they can be another creative tool, used to enhance subjects such as misty mornings and night shots, for example, and often most effective in black and white shots.

QUICK TIP

Try to get into the habit of checking the ISO setting each time before you start shooting or you may end up with a lot of pictures on a setting that does not suit the subject. Remember you can change your ISO at any time during a shoot – for instance, if the light drops suddenly and you find the shutter speed has become too slow for a hand-held camera, just turn up the ISO and retain your higher shutter speed.

LOW ISO

This is a small section taken out of a portrait to demonstrate the quality of image that is possible on a digital camera with a low ISO setting.

HIGH ISO

The section here is proportionally the same size in an image as the eye from the portrait, but the shot has been taken with a high ISO setting. While great effort is made by manufacturers to reduce grain and noise, it can be really attractive on some images.