Monday, June 22, 2015

Lessons from the Road: Part 2

In the last post I spoke about how big the US is: really big!

But it has other ‘extremes’, that get your attention. So from Carlsbad it was a not so quick drive over to White Sands National Monument, before another long journey home.

Because of the limited time we had, we ended up visiting White Sands after mid-day! Luckily I had thought ahead and had my IR converted 50D with me :-)

Wiki tells us that the White Sands gypsum is rarely found in the form of sand because it is water-soluble. Normally, rain would dissolve the gypsum and carry it to the sea. The Tularosa Basin is enclosed, meaning that it has no outlet to the sea and that rain that dissolves gypsum from the surrounding San Andres and Sacramento Mountains is trapped within the basin. Thus water either sinks into the ground or forms shallow pools which subsequently dry out and leave gypsum in a crystalline form, called selenite, on the surface.

Groundwater that does flow out of the Tularosa Basin flows south into the Hueco Basin. During the last ice age, a lake known as Lake Otero covered much of the basin. When it dried out, it left a large flat area of selenite crystals which is now the Alkali Flat. Another lake, Lake Lucero, at the southwest corner of the park, is a dry lake bed, at one of the lowest points of the basin, which occasionally fills with water.

The ground in the Alkali Flat and along Lake Lucero's shore is covered with selenite crystals which reach lengths of up to three feet. Weathering and erosion eventually breaks the crystals into sand-size grains that are carried away by the prevailing winds from the southwest, forming white dunes. The dunes constantly change shape and slowly move downwind. Since gypsum is water-soluble, the sand that composes the dunes may dissolve and cement together after rain, forming a layer of sand that is more solid and could affect wind resistance of dunes. This resistance does not prevent dunes from quickly covering the plants in their path. Some species of plants, however, can grow fast enough to avoid being buried by the dunes.

Various forms of dunes are found within the limits of White Sands. Dome dunes are found along the southwest margins of the field, transverse and barchan in the core of the field, and parabolic dunes occur in high numbers along the northern, southern, and northeastern margins. From the visitor centre at the entrance of the park, we drove the Dunes Drive, which leads 8 miles into the dunes.

Unlike dunes made of quartz-based sand crystals, the gypsum does not readily convert the sun's energy into heat and thus can be walked upon safely with bare feet, even in the hottest summer months. Which was good, as I laid down several times to get the best angle for a shot.

Although I knew we would be arriving at the worst time from a photography perspective, I hadn’t really prepared myself for the shock of the environment: its white heat!

The air temperature was 100F and the brightness meant I initially struggled to use my camera. My ‘old eyes’ and glasses meant that reading my camera controls was a challenge.

Luckily, once I had set things up, in the relative shade of our car, I was able to forget exposure and focusing, ie using a wide angle hyperfocal approach and Magic Lantern’s ETTR.

Although I used my IR converted 50D, I was not happy with the results: so no images to share. It is clear that the lens I’m using has a lens hot spot problem I need to sort out.

As for my trusty 5D3, here are three interpretations, eg playing around with WB, of a place that I would love to visit at sunrise or sunset.

Bottom line: any photographers who have not visited White Sands, should seek out this unique wonder of nature: but plan ahead and think about visiting at sunset or sunrise!

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