Specular Highlights
n addition to the very narrow depth of field for which close-up work is known, there is another close-up and macro phenomenon that most photographers either don’t know about or, at the very least, fail to exploit often enough. I’m referring to what are called specular highlights. These are most often seen as out-of-focus hexagonal shapes in either your background or foreground when shooting close-ups of subjects surrounded by bright highlights. A single dew-laden blade of grass surrounded by other dew-laden blades of grass that are all brightly lit up by the early-morning backlight is a perfect example of a subject that will yield specular highlights.
Specular highlights occur because any single or multiple light source that’s a part of your overall composition and is not in focus will assume the shape of the aperture. So, if your aperture is wide open, the specular highlights will be pretty close to round. If, however, your aperture is more closed down, the specular highlights will have more of a hexagonal shape, mirroring the shape of a smaller aperture opening.
With your macro lens or a focal length of between 40mm and 80mm, and in combination with a 25mm or 36mm extension tube, you’ll be quick to discover that when you focus on a single dew-covered blade of grass, each of those dewdrops functions like a tiny fish-eye lens. The surrounding landscape is recorded within each droplet. And if that fascinating discovery doesn’t quite get your attention, then surely all of those “diamonds” surrounding your one in-focus blade of grass will! You can’t help but notice them. These are the specular highlights, which are not quite round in the image opposite because they are taking on the shape of the aperture (which also was not perfectly round for this shot). All of these out-of-focus “drops of light” in front of and behind the focused subject are the reason why most of my students describe a morning of shooting backlit dewdrops as a “rich experience.”
To get this shot while on vacation with my family in Iowa a few years back, I scooted around freely, inch by inch, left and right, shooting a blade of grass here, a blade of grass there, each time resting my camera firmly on a small beanbag-type support as I made the exposure. For most of the images I made that morning in my wife’s aunt and uncle’s front yard, I shot between f/11 and f16, making a conscious effort to keep the camera and lens parallel to whichever lone blade of grass I was shooting. This assured me the maximum sharpness while still offering up an array of specular highlights.
Micro-Nikkor 70–180mm lens, f/13 for 1/40 sec.
When I made this image as evening approached, it was clear I wasn’t going to see the sunset in Tampa Bay, Florida. A big storm was heading my way. I chose to wait out the approaching thunderstorm in the safety of my rental van, thinking perhaps that if it cleared out quickly I still might have a chance at sunset. As the storm unleashed its fury, I took note of the powerful rain falling on the windshield and the urban yet stormy landscape beyond. With my Nikkor 35–70mm lens set to a 35mm focal length and its related macro setting, I was able to frame up a “wide-angle” shot that captured, close-up, the texture of the rain running down the windshield glass and the stormy background landscape behind.
At the same time, I noticed the traffic signal with its two red lights and quickly switched lenses, opting for my Micro-Nikkor 60mm. I then began to focus even closer on the rain-drenched windshield, choosing a point of view that included mainly the two traffic lights. As with more traditional specular highlights, when up close, these once small and distant lights changed into two completely out-of-focus red circles that contrasted nicely with the close-up, in-focus rain splatter on the windshield. And because I wanted these traffic lights to record as circular in shape, I needed to keep the aperture wide open, since it’s only at a wide-open (and most circular) aperture that an out-of-focus spot of light will record as a circle (rather than a hexagon) on your CCD or film.
Of course, as you have probably already figured out, I am always looking for unusual, nontraditional subjects—hence, these atypical specular highlights. If you want to capture highlights that are more traditional, other than Christmas lights or the Las Vegas Strip, I don’t know of a better subject for yielding a multitude of specular highlights than macro shots of dew-covered backlit blades of grass or spiderwebs shortly after sunrise (as here and here).
Left: Nikkor 35–70mm lens at 35mm; right: Micro-Nikkor 60mm lens, f/2.8, Aperture Priority mode
If diamonds aren’t exactly your thing, how about pearls? As I rounded a corner on a country road in Oregon’s Willamette Valley, I came upon a large field of dew-covered spiderwebs easily spotted against the backlight of sunrise. Once again, my ABS performed flawlessly as I quickly eased the car off onto the shoulder of the road and leapt into action with my camera and tripod.
Once that sun comes up, it doesn’t take long for the dew to dry up, so time is of the essence. I was quick to set up a composition that had me shooting at an angle to one of the many large webs in the field. Since I wanted to record a “string of pearls” surrounded by other out-of-focus strings of pearls, I set my aperture at wide open: f/2.8. With my focus thus limited to but a few strands of web, the out-of-focus strands recorded as circular specular highlights.
And did you notice the varied sizes of the specular highlight droplets? This is due to how close or how far each drop is from the plane of focus. The farther the dewdrops (the highlights) are from the plane of focus, the larger and more diffused they will become.
In addition, take note of the boxed areas marked A and B on the first image above. Box A shows the section of spiderweb on which I was focused. Box B is an area of shadow in the grasses behind and to the right of my spiderweb. In setting up my shot of the web itself, I made a deliberate choice to compose against that shadowed background area. I set my exposure for the much brighter backlit dewdrops, which in turn created a severe underexposure of that background, resulting in it recording as almost black. Just as in the jewelry stores, my pearls are showcased on a “piece of black velvet,” too!
Micro-Nikkor 105mm lens, f/2.8