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Big Bend '17: No. 8 - Welcoming the Night


The sunlight faded slowly, and the cold of a December night in the desert creeped in. The logical part of my brain said that we should hike the mile or so back to camp in the remaining light, but the photographer in me demanded that I wait on the exposed rim until the last rays of sunlight disappeared.


As the sun sank further beyond the horizon (or more accurately, as our position on earth rotated away from the sun), its light and warmth compressed into an ever thinner band of orange that faded precipitously into shades of cerulean sky falling from above. The once warm and vibrant desert now sank into a cold, blue haze. The landscape gradually gave way to the shimmering lights of small cities, campsites, and the occasional car traversing the desert below. The faint, terrestrial lights vaguely mirrored the stars that slowly gained a foothold in the sky above. Stars and lights alike twinkled slightly with the distortion of the heat still rising off the desert floor. Deep down we knew it was time to head back to camp for the night in the remaining twilight, but the photographer in me was unable to leave a perfect sunset until there was virtually nothing left for the camera to capture hand-held.



If I had hauled the tripod out to the Rim, I may have stayed longer to pull the last details of the sun and desert out, but fortunately for Travis (who is not as patient for photos as I am), the light had dropped off enough that my hand-held techniques were beginning to falter. I took a few bracketed photos to merge into HDR images, and finally gave up.


We always keep our headlamps in our packs, so we packed up, donned our equipment, and began hiking the mile or so required to make it back to camp. The nearly full moon provided more than enough light to see the trail back to SE1, but not enough to anticipate wildlife hiding in the tall grass flanking the trail. We turned our red lights on instead of white light to reduce headlamp-induced blindness, while still being able to see any glowing red eyes in the grass that may warrant our concern. It's always better to know where an animal is in the dark, instead of risking surprising them when they think they are hidden. It would be especially bad to surprise a Mountain Lion or a Bear, but even a seemingly benign animal like a Javelina (a small, wild pig) is dangerous when in fight or flight mode.



The campsites along the rim are nestled a hundred feet or so off the trail in order to provide some privacy and isolation. We reached the turn-off for our campsite without incident, but I couldn’t ignore the view of the desert below before we turned down the grassy path. A full moon and cloud cover are generally two of the greatest enemies of astrophotography, but sometimes the variable density of thin clouds backlit by the moon creates a unique night sky that is more than worth the time to try and capture it.



I crept out to the edge of the cliff on my stomach to help reduce the chance that one errant step on some loose rock might send me tumbling over the edge. I found a rocky ledge where I could balance the camera on my fleece beanie, and slowly worked on the orientation and focus for the shot which was very difficult given the low light and my position on the ground. As I took the 15 second exposures, I tried to shield the camera from the gusting winds that came up the side of the cliff.



Leveling and composing a shot at night is complicated by the painful reality that light drops off considerably when traveling through the body of a lens, most notably through the aperture. My zoom lens maxes out at f3.5, so even wide open, there isn't enough light to pick out any features even if I can see them easily with the naked eye. I generally aim the camera by looking down the barrel like a gun, and then estimate angle of rise. Sometimes I can use live view to help, but it can also be too bright to really help much, tends overheats the sensor causing noise, and has a less effective AF process that often can't focus at all in low light. I had to manually focus the lens in order to get a sharp image since the auto-focus was effectively useless in the dark.

How to Focus at Night - It's generally not possible to get a true infinity focus on an auto-focus lens just by turning the focus ring to the center of the infinity symbol like you can with most manual focus lenses. In order to provide fast auto-focus, and in order to facilitate the internal programming of the Nikon AF system, some play on the far ends of the focus range is required in order for the AF to verify max contrast by reaching a maximum contrast value, going beyond it where the contrast drops again, and then returning to the peak contrast value. This means that true infinity is hiding at some indiscriminate point in the range dubiously labeled as infinity. You generally cannot mark the focus range scale since it is locked away behind a clear pane, but you can use a white-out pen to mark where the center of the infinity symbol is after using the AF during the day on a high contrast object near a distant horizon. If you are focusing on something closer like a building or tree, you can always turn your headlamp on high just long enough for the camera to focus with the increased light, and then drop the light during the long exposure. Make sure to turn your AF to manual before taking a photo so it doesn't refocus, or remove focus from your shutter release and assign it to an Fn button (a process I may cover in a technical post later on).

I could have continued to take photos all night as the moon traversed the sky, but I knew it was already getting late and I planned to be up well before dawn to prepare for a tiny window of only a few minutes just before dawn where the moon would set to the Northwest just before the sun rose in the Southeast. I crawled back off the ledge, and headed back to the tent for a few hours of sleep before it was time to get up again.



© 2017-2018 Shaun C Tarpley

 
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