Plugged In: Low light calls for high attention to processing

  • The Kenai Fine Arts Center presents its free annual digital photography workshop and discussion, led by Joe Kashi, at 6 p.m. Friday, Oct. 18. Bring photos to share and discuss informally in this free, two-hour workshop. The Kenai Fine Arts Center, at 816 Cook Ave. in Old Town, will provide free bottled water, coffee, tea and cookies. Registration is not necessary.

By Joe Kashi, for the Redoubt Reporter

Now that you’ve taken all of those low-light holiday photos under adverse lighting, how do you make them look their best?

Before tackling that, let’s consider how to avoid unnecessary low-light photo problems.

Camera shake is the most frequent and serious concern adversely affecting low-light images. In last week’s article, we reviewed some camera equipment that’s effectively stabilized. That’s the single best way to reduce the problem, but it’s not enough. You’ll also need to use the fastest feasible shutter speed and brace yourself wherever possible.

As a result of some recent tests, I no longer believe that the best course is to use the slowest possible ISO or optimum lens aperture in these conditions while allowing a slower shutter speed to compensate with longer exposures. That approach worked several years ago when lenses and digital sensors were not as good.

Using base ISO and the optimum lens aperture works best in good light and is the best way to achieve the maximum possible image quality needed when making very large prints. However, holiday and other low-light situations are different. We don’t have enough light to achieve optimum image quality without using a tripod, which is quite the opposite of spontaneous photographs in social settings. Rather, we need to take the opposite approach.

Essentially all cameras have their best possible resolution and dynamic range at their lowest “base” ISO sensitivity setting. However, the modern cameras that we recommended last week do a more than adequate job at higher ISO sensitivities, at least through ISO 3200. At the same time, some of the best-suitable lenses, especially the Panasonic 20-mm f/1.7 and Olympus 17-mm f/1.8 optics for Micro Four-Thirds cameras, have a very bright maximum lens aperture and are very sharp at or near that bright maximum aperture.

As a result of these technical advances, I’ll now shoot most dim-light photographs at either ISO 1600 or ISO 3200, and use a lens aperture in the f/2.2 through f/2.8 range, with a correspondingly faster shutter speed, typically in the range of 1/20 to 1/30 of a second. I’ve found that this approach results in significantly sharper dim-light photographs. From that I deduce that, even with class-leading image stabilization hardware like that found in the Olympus OM-D E-M5, shutter speeds slower than about 1/8 to 1/10 second sometimes continue to cause subtly degraded sharpness due to very slight camera shake.

One additional factor — whenever you can, always shoot your photos in an RAW image format. Dim-light photographs usually need some help afterward through post-processing with good computer programs, like Adobe Lightroom or Photoshop. Using RAW image files allows vastly improved post-processing capabilities, and the final JPEG images that you make from RAW files will usually be much better, or at least more to your liking, than what most cameras produce by default.

You can set any RAW-capable camera to save each image in both RAW and standard JPEG formats in case you immediately need some images straight out of the camera. As a test, I suggest that you take some dim-light photographs in when set to RAW+JPEG, post-process the RAW files to your liking, and then see whether the straight-out-of-the-camera JPEGs are good enough under most circumstances.

Another important factor influencing good image quality is a camera’s dynamic range, its ability to simultaneously hold detail in both dark shadows and bright highlights. As ISO settings increase, dynamic range drops correspondingly. That’s a problem in bright sunlight with deep shadows and brilliant highlights, but not really a practical problem in typical dim-light social settings like holiday gatherings.

I’ve noticed that most dim-light social situations actually don’t have a really wide dynamic range. In fact, the opposite seems true more often than not. Even though our vision and brain compensate by making dim-light photos seem snappy and brighter than they really are, most such photos tend to be rather flat, with low contrast. In these cases, we need to adjust any photos to better depict what we saw, and remember seeing, in those situations.

The easiest solution to this problem is found in Adobe Lightroom. Use the “clarity” slider to adjust the contrast between adjacent parts of the photo. The “clarity” slider will also affect overall contrast, so you may also want to adjust the contrast slider to taste.

After adjusting overall clarity and contrast, adjust the exposure slider to taste. In low-contrast dim-light situations like these, many cameras will render the background at roughly the same brightness as the subject. That may look somewhat different than you recall the original situation, but it often cannot be easily avoided. In such instances, we depend on so-called “color contrast,” where separation between similarly bright (or dim) parts of the photograph is the result of their contrasting, or at least different, colors.

When lighting is highly directional, we may find that, as an example, one side of a subject’s face is brightly lit while the other side is heavily shadowed. That often results when dim light, low dynamic range and high ISO sensitivities combine to rob both highlight and shadow areas of important detail.

Again, the solution is found by post-processing RAW format image files. Using Lightroom, as an example, decrease the “highlight” slider to less than the neutral effect “0” midpoint while increasing the shadow detail slider by a positive amount above the “0” midpoint. Again, adjust to taste so that you have good detail and facial color in both areas.

Sometimes, though, this may not be enough. In such cases, use Lightroom’s adjustment brush feature to selectively reduce highlights and increase shadows by a combination of exposure, highlight/shadow suppression or enhancement, and clarity sliders in the adjustment brush subpanel. Each area will need separate adjustments. You may also need to add some noise suppression in any shadow area adjustments. Dark areas are more susceptible to digital noise, similar to snow in a weak TV signal, because of the lower signal-to-noise ratio in underexposed dark areas, particularly those that are boosted by post-processing.

Local attorney Joe Kashi received his bachelor’s and master’s degrees from MIT and his law degree from Georgetown University. Many of his technology and photography articles can be accessed through his website, http://www.kashilaw.com.

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