ISO

Film speed is a measure of photographic films sensitivity to light. The International Standards Organization’s (ISO) current standard of measuring this sensitivity for digital cameras is ISO 12232:2006. This standard has a number scale which indicates the digital camera’s sensitivity to light.

On the ISO scale lower numbers mean less sensitivity. An ISO of 100 is much less sensitive to light than a picture with an ISO setting of 1600. In situations where there is minimal light, you may find yourself with a completely open aperture and long shutter speed to capture a photograph. This comes with the possibility of camera shake (blurry subjects because the camera has moved during the long exposure). In this case a solution may be to increase your ISO setting. This however comes with a negative as well. As you increase your ISO pictures become grainier and has much less detail or sharpness than one taken with a lower ISO setting.

You may notice that there are trade offs to be made with aperture, shutter speed and ISO’s which is why there is a delicate balance to be made with all three settings. In nature photography you will often hear of photographers sacrificing graininess just to get the faster shutter speed when taking pictures of moving animals.