ISO 101: What is ISO and how do I use it?
ISO, which is sometimes pronounced “eye-so,” stands for International Organization of Standardization, which is an organization based in Switzerland that maintains a standardized measurement around the world for the sensitivity of camera sensors. Without some sort of standard measurement there would be inconsistencies between different brands like Nikon, Sony, Canon – or inconsistencies across different countries. It would be chaotic for photographers. ISO ensures that every camera you use will have the same measurement for its sensitivity to light.
As a quick overview of the mechanics of your camera… When you’re about to take a picture, light enters your lens and passes through the aperture (the opening inside your lens), and then it bounces off a mirror into the ‘pentaprism’ that directs the light to your viewfinder – which allows you to see what the shot will look like. So essentially, in a DSLR camera a series of mirrors directs light into your viewfinder.
When you click the shutter release, the mirror in your camera lifts up, so that the light isn’t redirected to the viewfinder. Behind that mirror, your camera’s sensor is blocked by a shutter, which opens very quickly to allow the light to reach the sensor.
When the light reaches your sensor, your “ISO setting” determines how much that light will affect the picture’s exposure. A lower ISO means that the sensor is less sensitive, resulting in a less exposed picture. A higher ISO means the opposite – the sensor is moresensitive and results in higher exposure.
ISO measurements generally land between 100 and 1,600 although some cameras go much higher, and some can go a little lower. While the specific steps can vary, you typically can go from 100 to 200 to 400 to 800 – and so on. Each time you double the number, you need half the amount of light to maintain a consistent exposure.
So what ISO setting should you use?
My standard practice is to keep my ISO as low as possible. Here’s why: the higher your ISO is, the more noise your photo will have (you know, that ugly graininess when you take photos at night). Now, you probably won’t see any noise if you keep your ISO around 100-400, but I always try to keep it as low as possible.
That’s where shutter speed and aperture come into play. Both of these settings also affect the exposure of your photo. So if you are taking photos with very little light and keep your ISO low, your photo will be underexposed – unless you adjust your shutter speed and aperture accordingly.
To understand aperture, check out this video, and be sure to subscribe to my YouTube, because my next video will be about shutter speed!
In summary, ISO is the standard measurement of how sensitive your camera’s sensor is. A low ISO means less exposure and vice versa. Try to keep your ISO low to avoid grainy photos, and just adjust your other settings to account for how much light you’re working with.
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Laura Pinckard is an intimate wedding and elopement photographer in the Adirondacks. She is based in Schroon Lake, NY but travels just about anywhere. Whether you're getting married in New York, the West Coast, or planning a destination wedding in Europe, feel free to reach out.