The latest digital cameras, with ISO settings of 1600, 3200 or as much as 6400, are amazing. It’s possible to shoot photos under many dark situations, where a flash has traditionally been used. The high ISO settings allow shooting photos under very little light.
Just a couple of years ago, shooting anything above an ISO 400 rendered pretty awful quality. During the last couple of years, camera manufacturers improve the density of the image chip, which allows good quality at high ISOs.
Many professional level cameras shooting at ISO 6400, look as good as ISO 400. In most situations, using these new cameras at ISO 6400, one could make great photos without the use of flash in normally lit rooms.
But using a flash combined with high ISOs is a better solution. At a recent wedding, the lighting was candles on tables, with one chandelier in the middle of the tent. By the end of the evening, there wasn’t enough light to make photos, even at ISO 6400.
At the beginning of the evening, there was enough light outside the tent, one could set the camera to auto everything for good background exposures. For detail in the faces, one simply adds a flash.
As night fell, the background exposure changed. To balance the background and hold detail in the faces, one could adjust the ISO on the camera to 800, later to 1200, and again to 6400 as the light outside the tent settled into night.
Without a flash, the subjects would be silhouetted against a bright tent. With a flash and variable ISOs, it held the detail in the faces and the background.
Another benefit for combining flash and high ISOs, one will notice longer battery life on the strobe.