Tips to Understanding ISO for Beginners
Ian Plant
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Understanding ISO takes patience, but it is the key to good photography. ISO stands for International Standards Organization, the standardized industry scale for measuring light. In Digital Photography, ISO measures the sensitivity of your camera’s image sensor. In this free video, world renowned outdoor photographer Ian Plant gives you guidance on understanding ISO. As he explains, the lower the ISO number the less sensitive your camera is to light and the finer the grain. Higher ISO settings are generally used in darker situations to get faster shutter speeds, but the images will suffer from digital noise and slightly degrade the quality. If you are in a shooting situation where the light is changing fast such as sports or wildlife, you might want to use your camera’s auto ISO setting.
ISO is basically a measure of your camera sensor's sensitivity to light. Most cameras have a base ISO of 100 or 200. And when you're shooting at this ISO, that's when you're gonna get the best image quality. But you'll have more options than just shooting at base ISO. Cameras will allow you to choose ISO 200, 400, 800, 1,600 and beyond.
And the higher you go, the more sensitivity to light your sensor has. And these higher ISOs can be useful when you're working in low light conditions. The trade off of using these higher ISOs is that you're gonna get something called digital noise. Basically when you're using these higher ISOs, you're pushing the sensor's ability to gather light, but you're doing it through artificial electronic means. And the result is, you get this pattern of grain that's introduced into the image and this grain will degrade image quality.
So the higher the ISO you use, the more light you can get, but the less quality you're gonna have. Every time you double your ISO numbers, say, go from maybe 100 to 200, you double your sensor's ability to gather light. And most cameras will give you the option of shooting ISOs as high as 4,000 or 6,400, or even higher. A lot of digital cameras these days do a pretty good job at correcting the digital noise even with these high ISOs, but all things being equal, you're gonna have better image quality the lower the ISO that you use. You also have the option of setting your ISO to the auto setting.
And I find this useful if I'm working in specific conditions where the light might be changing fast. So usually the only time I use auto is when I'm photographing wildlife and I'm working in conditions where the light is changing. That way I can just keep shooting and not think about the fact that the light is changing and have to change my ISO every time the light changes.
"Changing ISO changes camera sensitivity" is a common myth. There is no way to change detector sensitivity after the detector array is made. What changing ISO does is apply a variable gain factor to boost the signal. This gain factor obviously makes everything brighter which is why we increase ISO to higher levels in dark scenes. Applying the gain of course also boosts the noise levels so we have to watch out for that.