Plugged In: Low-light photography needs highly tuned skills

By Joe Kashi, for the Redoubt Reporter

Taking good photographs under low-light conditions requires better technique than taking the same photographs in bright sunshine. That’s our first topic this week.

Before starting our tips, it’s worth briefly recalling last week’s discussion about using the right sort of equipment when taking photos in dim light. Although too expensive for most of us, recent full-frame cameras, like the Nikon D800, when used with bright, wide aperture lenses, are optimal for dimly lit situations. They’re very usable up to ISO 6400 or so.

One step down, you’ll find very good low-light capabilities in the best APS-C and Micro Four-Thirds cameras, particularly the Nikon D7000 and D5100, the Pentax K-5 and K30, and Olympus’ OM-D and E-PL5, at least when using bright lenses with a maximum aperture of f/1.4 to f/2.5. These are quite good up to ISO 3200. Finally, a few better compact cameras with wide-aperture lenses do well up to ISO 800 or so. These include the Canon S110 and G15, Fujifilm XF and X10, Nikon P7700 and Olympus XZ-2.

You’ll encounter several problems when photographing without flash in dim light. These include camera shake, subject motion, slow focusing and difficult exposures. These can cause motion-induced blurring, which will probably ruin your photographs.

Although your digital camera’s potential photo quality is best at base ISO, rather than at higher sensitivities, using base ISO in dim-light situations typically results in blurred images. That’s due to subject motion and camera shake. Both are most severe at the very long exposures required by base ISO sensitivities.

As a result, dim-light photographs usually require higher ISO settings to get usable images not blurred by some sort of motion. Better high-ISO performance is the most important benefit to be gained by using modern cameras with large sensors. More recent cameras also tend to autofocus more reliably and quickly under low-light conditions, a common problem with older cameras.

Generally, more recent cameras include improved sensors that handle higher ISO settings before image quality becomes unusable due to increased noise and lower sharpness. As an example, my 2005-2006 Kodak P880 has an f/2.8 maximum lens aperture and makes truly lovely images in bright sunshine at its ISO 50 base sensitivity, but the P880 is unusable by ISO 200 and it was made before image-stabilization hardware became prevalent.

My 2011 Canon S100 has a maximum lens aperture of f/2.0, image stabilization and a better sensor no larger than the P880’s, but the newer Canon S100 makes good-quality images up to ISO 800. The S100’s brighter lens, image stabilization and improved high ISO sensitivities translate into an ability to use shutter speeds 16 to 32 times faster, depending on the circumstances. That can make all the difference when the light’s dim.

v So, our first tip is to test your camera in dim light and determine the highest ISO setting that gives you adequate image quality. Use that ISO setting when taking photos in dim light. You should also use your camera’s RAW image file format whenever available, because RAW allows you to later correct many potential defects that occur under low-light conditions.

v Next, determine whether your subject is likely to move quickly. If your subject is relatively motionless, then use a tripod, a monopod, or find a place where you can rest and steady your hands and camera. Be sure that image stabilization is turned on if you are handholding the camera, and turned off if you are using a tripod. When feasible, use a remote release.

v If you’re using a tripod, also activate the camera’s self-timer and set a two- to 10-second delay. That helps reduce camera vibration caused by pressing the shutter release too sharply and, if you’re using a digital SLR camera, also reduces the camera vibration caused by the moving mirror hitting its upper stop. Take exposure-bracketed bursts of several photos and then choose the least blurred image. It’s likely that at least one of them will show less motion-induced blurring.

v If you’re taking photos of frequently moving subjects, for example, at a child’s birthday party, then subject motion will likely be your most serious problem. If you’re within the range of your camera’s electronic flash, then try using a faster shutter speed and the flash unit, whose light lasts for 1/1000 second or less, fast enough to freeze almost any routine motion. Using flash effectively takes some experience, so practice before that birthday party.

v On the other hand, some subject motion has predictable pauses. I’ve often taken photos of students receiving their next belt at the Peninsula Martial Arts karate dojo in Soldotna. Until I learned to anticipate when students would be relatively motionless while bowing and receiving their belts, I found far too many photos were unusable due to blurring, even at a 1/40 second shutter speed. Again, if your camera has the ability to shoot many photos per second, then shoot a burst of several photos. It’s likely that at least one will not be too blurry to be usable. Faster shutter speeds are thus key to getting good pictures in these circumstances, but faster shutter speeds are feasible in dim interior light only when your camera works well at high ISO sensitivities.

v Even though RAW file formats can be more readily computer-corrected later, it’s best to use exposure bracketing when feasible and then choose the best unblurred exposures for later post-processing. If you bracket exposures, then set your camera to the aperture-priority “A” mode and set a lens opening that’s about one-half to one full “stop” smaller than maximum. Your camera will then adjust its exposure by varying the shutter speed.

Not uncommonly, less-experienced users set their cameras to “Program” (P), “scene” or fully auto “green” modes whenever they use their cameras. These fully automatic modes often work better outdoors and in very bright light. However, some changes to the default settings can often help you get better photographs.

In the P mode, for instance, the camera typically sets an intermediate lens opening and consequently slower shutter speed. Using a wide-aperture lens and changing the settings to use a lens opening that’s only slightly smaller than maximum often results in a sufficiently fast shutter speed. If you’re a somewhat more advanced photographer, then use the shutter-speed priority mode, usually marked on your mode dial as “S” or “T.” Set your camera to its fastest usable ISO and the fastest shutter speed that allows you to stop down your lens about one-half to one full “stop” from maximum.

Using a slightly smaller lens opening reduces the optical defects that are most apparent at maximum aperture and also increases the area that’s in usably sharp focus, termed “depth of field.” Although a lens aperture that’s two stops below maximum usually results in best sharpness under optimum bright-light conditions, sharpness is lost if there’s any camera shake or subject motion. When in doubt, give priority to a faster shutter speed and higher ISO — you’re more likely to get photos that are at least usable, even if not theoretically optimum.

“Scene” modes often include low-light options. Unless you are a fairly knowledgeable photographer, one of these may be your best bet when photographing under dim light conditions. Again, experiment ahead of time and find what works best for you under your anticipated situation. Because the names and settings of different scene modes vary from maker to maker, no single recommendation will work for everyone. Your own testing will be your best guide.

Generally, low-light photographs require some later post-processing on your computer for best results. Assuming that you have used an RAW image file format, you will likely post-process the photos using Adobe Lightroom, Adobe Camera Raw and Photoshop/Photoshop Elements or Apple’s Aperture.

When post-processing low-light images, I first adjust overall exposure to deal with photos that seem too dark or too bright, and then use the “clarity” or micro-contrast control to improve apparent sharpness and help separate muddy tones in adjacent parts of the photo. Then I correct, in descending order, overall contrast, sharpening and noise reduction.

You’ll likely find that underexposed shadows show more noise but little sharp detail. You can effectively and selectively reduce the noise in those shadow areas using the correction brush tool found in Lightroom 4. Finally, adjust the black tone, shadow area, highlight and white tone sliders found in Lightroom (or comparable tone and contrast adjustment tools in Photoshop and Aperture) to improve the visual impact of your image. Be particularly careful to avoid blowing out the highlights and thus losing any detail in them. If in doubt, give priority to retaining highlight detail rather than detail in the shadows.

Photographers taking close-up “macro” photographs often encounter technical issues quite similar to those occurring in low-light situations, so we’ll take up macro photography in the near future.

Local attorney Joe Kashi received his bachelor’s and master’s degrees from MIT and his law degree from Georgetown University. He has published many articles about computer technology, law practice and digital photography in national media since 1990. Many of his technology and photography articles can be accessed through his website, http://www.kashilaw.com.

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