Lesson Seven: The Sharpness Triad, Part III

So you've opened the aperture as wide as you can and you've set the appropriate shutter speed and you still can't get a sharp picture.  What can you do?  Well, as a last resort, you can try increasing the ISO.  What exactly does that do?  Well, it increases the sensitivity of the camera's sensor to light so you don't need to open the aperture as wide or keep the shutter open as long.  So you're probably asking yourself if it can do all that, why not just shoot constantly in the highest ISO your camera can shoot?  Well, it turns out that the higher the ISO (i.e. the more sensitive the sensor is to light), the more grainy the picture turns out which is not always a bad thing especially if that is the kind of look you're going for and, of course, a grainy picture is better than no picture at all.