By Joe Kashi, for the Redoubt Reporter
Improved low-light operation is probably the most useful practical enhancement to better digital cameras in the past five years. This week, we’ll take a first look at techniques to increase your chance of successfully capturing low-light opportunities.
With the 2010 introduction of Pentax’s K-5 and Nikon’s D7000, high-quality photographs shot at ISO 3200 became both feasible and affordable. By 2012, smaller, interchangeable-lens mirrorless cameras, like Olympus’ OM-D series and Fujifilm’s X-series, made comparably good low-light images. However, effective use of improved low-light capability does require some extra effort to realize those benefits under challenging conditions.
Digital technology has major low-light advantages compared to older film cameras. What we considered to be state-of-the-art technique during the film era, using unstabilized cameras at 1/30 second and black and white Tri-X film push-processed to ISO 1600, has become routine and reliable as stabilized large-sensor digital cameras have expanded our handheld, low-light frontier. Now, good-quality color images are readily captured at ISO 6400 and 1/8 second, a four-EV improvement that’s impressive given the more forgiving nature of digital color imaging.
Improved print quality has kept pace. Push-processed, 35-mm film negatives could be printed no larger than letter size before noticeably losing fine detail and image quality, while high-ISO digital images can maintain good image quality when printed many times larger.
By definition, low-light photography occurs on the thin edge of too-slow shutter speeds, too-high ISO settings and too-wide lens apertures, all of which tend to reduce the crisp resolution of images. With the right combination of modern gear and good technique, though, you can avoid many low-light limitations.
First, determine how you’re likely to use your low-light photos. If you’re only posting relatively low-resolution casual images to websites like Facebook, then the most important consideration is avoiding obvious blurring caused by camera shake. Almost any recent, large-sensor digital SLR or mirrorless system camera with decent image stabilization should work for casual low-light use.
Low-resolution JPEG images for Internet use and newspaper reproduction are best made by later “downsizing” a camera’s originally high-resolution RAW image file with software like Photoshop or Lightroom. When a file is downsized and then saved as a reduced-pixel image, noise and slight blurring become less evident. Blurring from significant camera shake, though, remains noticeable, especially when small light sources within the image leave a multitude of bright “star trails.” Downsizing an originally high-resolution photo almost always produces a better low-resolution JPEG image than using your camera in its low-resolution mode.
However, if you’re shooting a wedding in a dim banquet hall or making fine art photographs, as examples, then technical requirements become more stringent. You’ll need high-quality, full-resolution results regardless of lighting conditions.
Although full-frame digital cameras as a general rule have the best high ISO performance, most current full-frame models have a number of limitations that partially negate their inherently better high-ISO capabilities. In low-light conditions, I prefer smaller cameras with high-efficiency, in-body image-stabilization hardware and bright, single-magnification “prime” lenses. I use and particularly like Pentax’s K-5 IIs and Olympus’ OM-D E-M5 cameras because of their excellent, 16-megapixel sensors and very effective in-body image stabilization hardware.
In addition to brighter maximum apertures, prime lenses have several other advantages for low-light photography. Good prime lenses are usually sharper than zoom lenses at the wide, bright apertures you’ll need when the light’s dim. Prime lenses also tend to produce higher contrast, “crisper” images, a trait often needed for low-light conditions. Primes are usually smaller and lighter, which may reduce fatigue and camera shake with prolonged use.
Regardless of the camera and lens you choose for low-light work, your first step should include making some tests to determine the slowest shutter speed, widest lens aperture and highest ISO sensitivity that can be reliably used under varying conditions. Test both automatic and manual focus to determine which is most accurate in low light. At wide apertures, depth of field — and, thus, your margin for focusing error — is razor thin.
With that testing data, you’ll know the limits of your gear and which settings are the least likely to cause problems in low-light conditions when handholding your camera. Make some tests, as well, to determine the largest print sizes that retain high image quality with a variety of ISO settings.
A tripod and delayed shutter release are best, of course, for long, dim-light exposures, but that’s not always practical, especially in social settings. With modern image-stabilization hardware, like the five-axis systems used in upper-tier Olympus cameras, and Sony’s newest A7 II full-frame models, it’s possible to get sharp, handheld photos of static subjects with shutter speeds as slow as 1/6 second to 1/10 second, depending on lens magnification. Remember that telephoto lenses magnify not only distant subjects but also blurring from camera shake.
Expect that a majority of handheld images made at very slow shutter speeds will have at least a minor amount of blur due to slight camera shake, even with good image stabilization. When capturing fine detail is important, take a number of additional shots of that image. It’s likely that at least one will be steady enough to show needed fine detail. Shooting extra frames is good insurance.
If you can avoid camera shake, upper-end cameras and lenses are capable of making sharp images at high-ISO sensitivities, but blurring due to camera shake is uncorrectable. Although it’s usually best to set the lowest ISO sensitivity that allows for a fast-enough shutter speed, if in doubt, increase your ISO setting and accept some additional image noise rather than risking a too-slow shutter speed that’s likely to blur. If possible, brace yourself against something solid, such as a wall, and then gently press the shutter release rather than jab it, which creates a rotational camera motion.
Exposing and post-processing low-light photos can be tricky, so we’ll save that topic for next week.
Local attorney Joe Kashi received 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.