1. Use the Maximum Aperture
Opening up to the widest available aperture—denoted by the smallest f/number—allows as much light into the camera as possible. That’s what you want in low light, after all. If you’re in shutter priority, switch to a different exposure mode—like manual mode or aperture priority. In any auto mode, you have to be careful about your settings to ensure you’re not working against your own interests by trying to shoot in low light at, say, ƒ/11. That aperture might be ideal on a bright sunny day, but in low light, you’re just making it harder on yourself if you’re not wide open—or at least close to it. In aperture priority exposure mode, set your aperture to the maximum (ƒ/2, for instance) and the camera will choose the appropriate corresponding shutter speed. In manual mode, dial in the wide-open aperture and then watch the meter to choose the appropriate corresponding shutter speed. Or in live view mode, watch the LCD as you adjust the shutter speed to make the correct exposure. However you decide to get there, starting with a wide-open aperture ensures you’re allowing as much light into the camera as possible, which corresponds to a faster shutter speed—one of the main things you need when working in low light. The only downside is if you want greater depth of field, a wide aperture won’t achieve it.
2. Use a Tripod and a Slow Shutter Speed
What defines slow? That’s relative, and it depends on just how “low” the light is. It also depends on what you’re shooting. A landscape at dusk, for instance, or an architectural photo? No problem; use as slow a shutter speed as you’d like. Those subjects aren’t moving, after all, so they’ll be sharp as long as your camera is locked down to a tripod. But if you’re trying to shoot a portrait or any sort of action photography, any shutter speed below 1/30th is likely to be unusably blurry. In these situations, you’re simply going to have to choose another option—like adding a flash.
3. Add a flash. Using a strobe—either attached to the camera or preferably (because it improves the quality of light) away from the camera on a light stand—is the simplest, most straightforward way to rectify a low-light situation without sacrificing depth of field or subjecting your subject to long exposures. Not enough light? Add some more! It makes perfect sense in a lot of ways, but it does have some drawbacks. Namely, it changes the look of the scene. Done well, it can make a scene look beautiful. But flash on camera isn’t typically about beauty so much as creating an adequate exposure. So when you’re faced with this kind of situation and your only option for adding light is an on-camera flash, consider diffusing it or, better still, aiming the flash up (instead of directly at the subject) to bounce it off of a white ceiling and make the light bigger, broader, softer and generally more attractive.
4. Crank the ISO
This option, in my opinion, provides the best of both worlds and allows the photographer to work with the shutter speed they want and at the appropriate aperture to achieve the depth of field they need. In the old days, ISOs higher than 1,600 were incredibly noisy. But some of the biggest innovations in sensor technology in the past decade have come in the form of low noise at very high ISOs. Where magazines such as National Geographic once limited photographers to ISO 400 for double-truck images, now photographers can shoot at ISO 4,000 with similar—if not better—results. With every passing generation of cameras, it seems that already great signal-to-noise ratio gets even better, making ISOs of 6,400 and 12,800 downright reasonable in low-light situations. Best of all, increasing the ISO allows photographers to shoot without adding additional light, which inevitably changes the look of the scene. No flash and a high ISO has the added benefit, in many cases, of making pictures more interesting and more colorful. How? Because when working with a flash in low light, often the flash illuminates the subject but not the background—so the background goes dark. Instead of a subject isolated against a dark or even black background, a higher ISO allows whatever illumination—and color—in the background to shine through. One way to achieve the appropriate ISO is to use the auto ISO setting. Simply dial in the aperture and shutter speed combination you need—say, 1/250th at ƒ/8—and the camera will raise the ISO to the necessary level for a correct exposure at those settings.
5. Fix it in Post
No, this isn’t an ideal option. But if all your other options are exhausted, you’ve gotta do what you’ve gotta do. It’s better to get the shot than miss it, after all. Assuming you’re capturing RAW image files, you’ve got a lot of exposure latitude built into your files. So even if the correct exposure is, say, 1/60th at ƒ/2 at ISO 12,800, but you feel that you don’t want to go above ISO 3,200, shoot it two stops underexposed and fix it in post. You’ll be amazed at what happens with that RAW image file when you bring it into Lightroom and adjust the exposure. By simply dragging the exposure slider, you’ll turn that underexposed image into a normal exposure—almost as if you’d done it in camera. In fact, I’d argue that all you’re doing here is amplifying the signal and the noise as you would had you cranked up the ISO two stops in the first place. You’ll still need to do some post-production noise reduction, but better to have a sharp, noisy capture of the perfect moment than a blurry version or, worse, missing the shot altogether. If for any reason you’re underexposed in low light, try salvaging the image in post. As long as you shoot RAW, you’ll be amazed by just how much information you can pull out of those dark shadows.