How to Use Your Digital Camera's ISO Setting

The ISO setting is a critical control common to all digital cameras. Mastering it can greatly improve your photographs, whether you're shooting from a tripod or trying to make the most of unfavourable lighting conditions.


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    Plug your headphones into an amplifier connected to your computer or MP3 player and listen very carefully. (Don't worry, this is going somewhere.) Keep the volume down on your computer or MP3 player and then turn up the volume on the amplifier. You'll notice that while your music gets louder, noise (usually a gentle hissing sound) gets louder as well.

    This is not entirely dissimilar to the function of your ISO setting! Your digital camera's sensor only has one inherent sensitivity, which is its actual physical sensitivity to light hitting it. If a picture is too dark (as will happen with a too-slow shutter speed), then your digital camera can amplify the signal from the sensor, just as you can turn the volume up on your amplifier to make your music louder. The downside is, just as with your music, amplifying the signal also increases the amount of noise (grain) in your photographs. So there is a trade-off: if you want faster shutter speeds, you'll have to increase your ISO ("turn up the volume"), at the cost of bringing out noise. We'll explore these trade-offs some more.
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    Find your ISO control. This is usually buried in the menus on compact cameras, and most digital SLRs have a dedicated button for the setting. Check your camera's manual if you can't find it for yourself. Now see the various ISO settings you have available. Digital SLRs will usually start at 100 or 200 and go up to 1600 and beyond, compact cameras will have a much smaller range of values.
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    Shoot your camera outdoors in P(program) mode. Take a shot at each of your available ISO settings then look at them on a computer. Every camera will look different, but you'll find that the higher settings the image will either become noisier, softer (due to noise-reduction being applied in-camera), or both.

    While looking at your shots, compare the amount of noise and see what shots you think are ISOs you will always be able to use, which you will use if the circumstances merit it, and which you'll try your best to avoid using. Only you can decide this; every camera is different and tastes differ wildly too.
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    Shoot your camera in shutter priority mode to make some more tests. What you want to find out is which shutter speeds will get you perfectly sharp shots every time. Note your focal length, which is in millimeters. Shoot the same scene, but at a variety of shutter speeds, going down to half a second or thereabouts. Some people have very steady hands and technique and can shoot at very slow speeds, others less so.

    Now, find the shot from the ones you took with the slowest shutter speed that gave sharp results, and then remember this number as a factor of your focal length. So if your lens was at 30mm and you could shoot sharp photographs hand-held at 1/15 second, then you'll need to increase your ISO if your shutter speed drops below half of your focal length of whatever lens you were using.

    Remember: faster shutter speeds don't just freeze motion, they also reduce the likelihood of camera shake. A noisy but sharp image is much better than a noise-less image that has been blurred by camera shake.
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    Don't worry about this if you're shooting still subjects from a tripod. If this is the case, use the lowest setting you have. You only need to crank up your ISO if you need a faster shutter speed than would otherwise be available under the lighting conditions. This isn't important if your subject doesn't move and if there's no issues with camera shake from shooting hand-held.
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    Don't worry about this in bright daylight either. Unless you're using massive telephoto lenses, you'll have more than enough light to grab whatever shutter speed you need. Keep your ISO low and you'll be fine.
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    Decide if there is motion to freeze and act accordingly. We're talking subject motion and not camera shake here. This is mostly of concern to people shooting sports indoors or under dim light. A shutter speed of 1/250 will freeze most things, and 1/500 many more things, but the exact speeds for certain kinds of subjects will be learned by trial and error.

    Keep an eye on your shutter speed: if it drops below the desired number, increase your ISO until you get a shutter speed fast enough to freeze that motion. Likewise, if your shutter speed goes much faster than you require, consider decreasing your ISO in order to get the cleanest shot possible.
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    Use your ISO control to avoid camera shake for hand-held stills. You hopefully made some tests earlier to figure out at which speeds you are able to hand-hold a lens of a certain focal length (if not, make some now!). Once again, noisy sharp shots are better than blurry clean shots, so don't hesitate to crank up your ISO to get whatever shutter speed you need.


  • You probably shouldn't be taking very many practice pictures (blurry ones) at any event (if you're shooting one), so practice beforehand. Practice ahead of the event, to get your exposure right, though, then just make tweaks accordingly.
  • The recommended ISOs are not absolutes for different environments, so don't be afraid to experiment a bit. It can be frustrating when you don't get it right, but in time you will learn what works best with your camera.
  • Unless you adjust the aperture and shutter speed accordingly, 100 or 200 are good for a sunny day, 200 or 400 are good for a cloudy day, and for indoors it's anywhere from 100 to 1600 to 6400, etc. The higher the number, the brighter the picture.
  • Canon or Nikon DSLR camera: Use on one of the semi-auto modes (AV, TV, or P on Canon), or on Manual (Manual works best, because it's easier when you're in control of the camera, rather than vice versa), go to the menu where ISO settings are located (for a Nikon) or the ISO button (for Canon). The numbers range anywhere from 50 or 100 to very high numbers, usually 1600, or 6400. The smaller the number is, the less bright your picture will be.
  • If you're in AV mode for Canon, it lets you adjust the ISO, the rest is automatic. This is probably the best mode to be in if you only want to adjust the ISO.

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Categories: Digital Photography