Shooting in low light situations is difficult. It presents a combination of problems for which there is no single quick fix. You can decrease the shutter speed, but if you don’t have a tripod, your image will be blurry. You can bring a flash with you, but if you’re too close to your subject, you’ll overexpose the shot. And you can always open up the aperture, but when you do that, you lose your depth of field.
Thankfully, there’s one more setting you can adjust for better results in low light situations. That setting is your camera’s ISO speed. By adjusting this setting, you can increase the speed at which your camera’s image sensor takes in light from the outside world. The faster it goes, the more light your camera takes in, and the brighter your pictures become. Simple as that.
What is ISO Speed?
ISO speed gets its roots from film photography. All film used in film cameras has a certain film speed, which is a chemical property of the film that determines its responsiveness to light. Faster films, much like faster ISO speeds, take in light faster and result in brighter images.
When the first digital cameras were being developed, the camera companies wanted them to function almost exactly like their film predecessors. That’s why today’s cameras have ISO speed settings. Photographers are used to working with films that have a certain film speed, so if you can engineer a camera to mimic film speed, you destroy one more barrier to the widespread adoption of digital cameras. The digital camera becomes much more familiar, and professional photographers adopt it faster.
Why change the ISO Speed?
The number one reason photographers change the ISO speed is to counter blurriness in their images. When you’re shooting low light, you usually have to use slow shutter speeds to get the right amount of brightness. But this creates a problem. Your pictures become more susceptible to blurring created by camera shake.
When you increase your ISO speed, you can then increase your shutter speed and get the same brightness. This counteracts the blurring and gives you the best of both worlds.
What does ISO speed do in Automatic Mode?
You usually can’t control much in automatic or programmed automatic modes, but some cameras will allow you to adjust the ISO speed. This is handy when you’re shooting action toward the end of the day. As the light goes down, your camera automatically picks slower shutter speeds to compensate. This will cause blurring (especially in sports).
If you increase the ISO speed from the main menu, your camera becomes more sensitive to light. Another way to think of it is you are “fooling” your camera into thinking it’s brighter outside. Your camera will then pick a faster shutter speed, and you’ll get the desired result. So if you’re shooting in programmed automatic mode, and you’re getting a lot of unwanted motion blur, go ahead and increase your ISO speed.
How else can you use ISO speed to improve your photography?
It’s ideal to change your camera’s ISO speed whenever you need a tiny bit more light to get the shot right. Let’s say you’re indoors, and you want to take some pictures of your friends without using the flash. You’ve tried to take the pictures using a slow shutter speed, but it didn’t work because the camera was shaking while the pictures were being taken, and everything came out blurry.
If you increase the ISO speed, you can increase your shutter speed without making the image too dark. This gets rid of the blurriness that often results from camera shake. Increasing the ISO speed is sort of equivalent to increasing the total amount of light available in the scene. It allows you to get away with faster shutter speeds or narrower apertures as if there were more light coming through the lens.
ISO speeds and different shooting situations
For those of you who aren’t too familiar with ISO speed settings, I’ve compiled a quick list of different ISO speed settings and when you’ll want to use them.
ISO 100. This is the default ISO speed setting on most cameras. It is also the lowest setting. At ISO speed 100, you get the maximum sharpness and color from your images. Use it when you’ve got plenty of available light and no possible blurring issues.
ISO 200. The next step up. At ISO 200, your camera is twice as sensitive to external light as it is at ISO speed 100. If you wanted to get the same brightness, you could increase your ISO speed from 100 to 200 and increase your shutter speed by one setting/stop.
ISO 800. Starting to get into the mid-range of ISO speeds. I often use this one when I’m shooting in a mostly well lit room, but I need a little extra kick to get a somewhat faster shutter speed. You’ll start noticing a slight increase in graininess here.
ISO 3200. The maximum ISO speed setting for most cameras. Use this at your own discretion when you have no other options for external lighting. At this setting, your images will turn out quite grainy. Sometimes that’s better than blurring. Sometimes it isn’t.
Is there a downside to increasing the ISO speed?
Unfortunately, yes. Because your camera’s image sensor lets light in faster, it loses some accuracy. This manifests itself as noise or grains on the image itself. If you can imagine television static superimposed on your image in a faint kind of way, you’ll get the idea.
As you ratchet up your camera’s ISO speed, you ratchet up the noise. That’s why it’s important to avoid going overboard whenever you adjust ISO speed. Increase it too much, and the resulting image will look too grainy. Most of the time, a few settings higher is enough to get a much-needed boost of brightness.
The lower you go, the better your colors turn out. Lower ISO speeds also make your images sharper and less grainy. If you have more then enough light, always set your ISO speed to the minimum value on your camera. As a matter of fact, some of the newer camera models feature some of the lowest ISO speed settings I’ve seen. It’s all in an effort to give photographers more color and extra sharpness.
When to adjust something else
It’s also important to know when you should adjust something else instead of the ISO speed. If a few ISO speed settings higher won’t get you to that happy place, you might need to consider moving to a brighter shooting location, bringing in some extra light, using a better external flash, or using a tripod. Each of these solutions will, of course, have its advantages and disadvantages.
Graininess as an artistic effect
You can also use the high ISO speed graininess to your advantage. Grainy photos have a kind old-timey avant-garde look to them. This is especially true when you shoot in black and white. The low fi quality will bring your viewers back to the days before fancy Nikons and Canons, when you took pictures of your dog with a Holga and called it a day. It’s nice to add a few of these shots to your portfolio just to have something different.
Got any questions about ISO speed? Has it saved your neck before? Have you used the graininess for artistic effect? Let me know or leave your comments below.