Zoom Zoom: ISO

Back in the day, before SD cards, cameras used a kind of memory stick that usually came in a little canister and they called it film. Different kinds of film had different speeds, indicating how much light it needed for exposure. “Faster” film required less light, but was grainier and “slow” film required more light but had better quality.

Today, digital cameras usually have a setting called ISO which controls the sensitivity of the sensor. Although the technology is totally different, the effect is the same. Lower ISO gives better image quality, using higher ISO lets you get photos in lower light (or with a faster shutter speed), but makes your images noisier.

ISO is one area in which cameras vary widely. Newer cameras are much better at taking decent images at higher ISO and cameras with small sensors, like point and shoot cameras, are often pretty bad (although also improving every year). For this reason, I can’t specify the proper ISO. In general, though, use low ISO if you can, and test your camera to see what ISO settings still produce usable images.

If you look closely, you can see the graininess of this high-ISO photo.
If you look closely (click to enlarge), you can see the graininess of this high-ISO photo.

Also, keep in mind, if you are cropping an image, high-ISO noise will be much more noticeable, and if you do lots of adjustments to your photos on the computer, many of these, like sharpening, may make high-ISO noise even more apparent. And, of course, if you are making images primarily for sharing in low resolution online, noise from using a high ISO may not be visible at all.

Sharpening accentuates noise from using a high ISO.
Sharpening accentuates noise from using a high ISO.

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