Balancing act

In a dark environment like this dawn shot in Venice, you have to raise the ISO in order to balance the exposure on the flashed subject with the background and, at the same time, get a sharp picture throughout. If the ISO is too low, the foreground and background can balanced with respect to exposure but the shutter speed will be slow, thus possibly blurring the background and causing a ghosting on the subject. This is true unless you use a tripod, as I did here. Then the shutter can be longer assuming the subject can be perfectly still. The higher the ISO, the shorter the exposure time which obviously prevents the subject from being less than sharp. But the higher the ISO, the more noise is created, too. So, it's a balancing act. During carnival we get up in the pre-dawn to photographed the costumed models because all the non-photographer tourists are still in bed and we can get perfect backgrounds behind the models. My settings for this picture were one second, f/13, 1250 ISO. I used a 24-105mm lens.