What is ISO?
ISO represents the sensitivity of your camera sensor to light. For those of you close to my age, you might remember the old term ASA. Same thing. ISO can vary from 100 to as high as 25,000 or more on some of the digital SLRs and mirrorless cameras. The bigger the number, the more light sensed.
How does ISO affect a photo?
Why not just go for the biggest setting and be done with it? Well, just like with film, there is a trade-off for that sensitivity. In film it was called grain, in digital terms it is noise. The higher the ISO, the more noise you will get. So you will want to keep the setting as low as possible. Preferably at 100. But what if you can’t? What if it is too dark and you can’t use flash? Well, if you must, use a higher setting. But do so knowing that you are compromising the quality of your photographs in favor of getting a picture versus not getting it any all. And, there is one thing you can do to decrease the noise significantly. Where it is located varies by camera, but there is a camera setting for automatic noise reduction. It helps a lot. The problem is that as usual there is a price, a trade-off. Whatever shutter speed you use, it will take at least that long for the noise reduction algorithm to work. That is because it takes a totally black picture right after the actual exposure, and looks for false sensitivity readings. It then subtracts out that noise from your photograph. Much better, but it will really slow things down sometimes, and it could totally prevent you from using Burst Mode, also known as Continuous Mode.
What is a good ISO range for a camera?
It is important that you not leave your camera on the default setting for ISO. That default setting is Auto ISO, which means the camera will potentially choose a very ISO. Yes, you will get the photograph, but will you want to use it for anything? Better to be forced to set it manually so that you can consciously make choices about how to get the best quality photograph you can under the existing conditions.
How can I tell what is the best ISO for my camera?
Try this exercise: There have been significant advances in noise reduction in the newer digital cameras. Take a number of photographs of the same object, under the same lighting conditions, while varying the ISO settings. Look at these photographs on your computer monitor. But go beyond the size of your monitor. Enlarge them, and look for “grain.” Determine where the quality begins to deteriorate. That will be an important discovery for use in taking low light photographs in the future. Digital cameras are improving at a fast pace. ISO settings are able to be set higher and higher without much noise. Find out what works for you. But look at the photographs at a high magnification. Consider what the results will be if you get that great shot and want to print it poster sized. That is an option that is now very affordable, so don’t rule it out.