Let’s talk about ISO and what that entails. You’ve got your memory card in, your camera is on. You’ve selected your program mode. All that’s left to do is to select your ISO.
ISO is a standard acronym that came from the film days. It is also known as ASA. All the digital manufacturers decided to keep it. What it means is, basically, is how sensitive the sensor is going to be the light. If you are a film shooter, you remember you having to choose your film’s “speed.” Color film was available in ISO 100, 200, 400, 800 or 1600.
So if your ISO is at 100, it’s going to be less sensitive to light than at 1600. The advantage of setting your camera to a lower ISO is that it’s going to be a lot cleaner of an image. They don’t look grainy with digital “noise.”
You want to keep your ISO setting as low as possible, and it’s fairly easy to figure out how low you can go. If you go outside in the dark with ISO 100, your picture will come out black. ISO 100 is for sunny days. ISO 400 is for cloudy days. If you’re indoors but some existing light, especially with these high end DSLRs, ISO 800 might be sufficient with no flash.
There is a lot of value to taking the image with no flash. It’s more of a natural light. It’s a softer light and a lot more pleasing to the eye than a flashed image with no modification to the flash.
You can also use the Auto ISO, which most newer cameras have. Your camera will decide what ISO to choose, and normally does a good job, but it’s not as much fun as experimenting.