Tuesday, February 2, 2016

Seize the Fleeting Light (Exposure)

Cameras have been around for so long—almost two centuries—and have become so common that we take them for granted. But how remarkable to capture light and create an image with it! We can preserve a fleeting moment, a scene we’ll never see again, a friend soon gone. Sometimes when I’m struggling with a difficult shot and feeling exasperated, I contemplate this miracle, trying to create the excitement that the early photographers experienced:
“I have seized the fleeting light and imprisoned it! I have forced the sun to paint pictures for me!” LJM Dagurre, ca. 1835
The camera at its simplest: light reflected by the tree passes through a small opening, and creates an inverted image on a surface (source). If the image is to be preserved, the surface must be light-sensitive.
As the camera evolved, the basic structure remained the same: a light-proof box with a small opening, a lens to bring the captured rays into sharp focus, and a light-sensitive surface (today's digital sensor) which is exposed just long enough to capture the image.
Modified from source.

• • •

In 1870, photographer William Henry Jackson traveled for three months through the southern part of Wyoming Territory, on an expedition led by geologist Ferdinand Vandeveer Hayden. He took on the order of 200 photos, using the popular medium of the day—wet plates. Their greater sensitivity allowed significantly shorter exposure times, but they were hardly convenient. For one thing, a field photographer had to carry a darkroom to prepare and process the plates!
Jackson’s photographic gear was transported in an ambulance (small wagon) and on a mule named “Hypo”—for sodium hyposulfite, the popular photographic fixer of the day (source).

In mid-August, Jackson and four others made several side trips into the Laramie Mountains. He took photos of the rocky range with its odd granite outcrops—described by Hayden in his 1871 report:
… the red feldspathic granites rise in thick picturesque ridges, fifty to one hundred feet high, like ruined walls, lending a peculiar as well as picturesque appearance to the landscape.”
Granite rocks, at foot of Laramie Peak; William Henry Jackson, 1870 (source).
Granite rocks, southern Laramie Mountains; 2016.
Upon reaching a suitable vantage point, Jackson would set up the camera and darkroom—actually a dark box. He cut a 6.5” x 8.5” glass plate, and cleaned it carefully. Kneeling before the darkroom, in a cloth-covered frame with a bag-like opening for his head and shoulders, he poured a thick syrupy (and combustible) liquid on the plate, tilted it in various directions to get an even coat, and let the emulsion dry just enough to stay in place. The wet plate was placed in a dark cover, and carried to the camera.

Before installing the wet plate, Jackson brought the image into focus. He removed the lens cap, casting an inverted image on a sheet of ground glass. After adjusting the distance between image and lens, he put the cap back on, and replaced the ground glass with the wet plate. Then he removed the lens cap and started counting.

Jackson needed enough light to reveal the details of the scene, but if he captured too much, the image would be washed out—overexposed. He took into consideration the brightness of the day, the light coming off the subject, the degree of detail desired, past experience and a sizable dose of intuition. An exposure on the order of five seconds often worked well for landscapes, but sometimes exposures were measured in minutes.

The exposed plate was put back in the dark cover, taken to the darkroom, and developed to reveal the captured image. It was fixed in a bath of hyposulfite, and examined to see if the exposure had been correct.
“The art of timing exposures was still so uncertain that one prayed every time the lens was uncapped, and no picture was a safe bet until the plate had been developed.” (from Jackson & Driggs 1929)
Granite ridges near the eastern base of Laramie Peak; William Henry Jackson, 1870 (source). Click on image to view the horse-drawn ambulance carrying photography gear.
The difficulties endured by Jackson and other early explorer-photographers seem onerous today. But their efforts were justified. Photographs were still novel and in great demand, especially given the time and place. Much of the American West was wild undeveloped country. Photos could show spectacular landscapes to people who would never be able to visit themselves ... miraculous!
Granite rocks, southern Laramie Mountains; 2016.
The Sherman granite is about 1.5 billion years old. It was intruded soon after a continental fragment collided with what was then the south coast of North America.

Like Jackson, I’ve made trips into the Laramie Mountains to take photos. And like Jackson, I have to be careful about the amount of light I seize. But there's no counting, no guessing, no waiting until the image is developed and fixed to see if the exposure was correct. It's so much easier with my digital camera—most of the time.

In Auto mode, I simply compose and press the shutter button halfway down. The camera quickly makes measurements, calculations and choices. Then I push the button the rest of the way to seize the light and create an image. Occasionally I change certain settings: smaller aperture for greater depth of field; or faster shutter speed for a moving subject. The camera adjusts other parameters to maintain a correct exposure.

As I know from experience, my camera usually makes the right choices. In fact, most of the time it performs far better than I could ever hope to! But not always. Some scenes defy its metering system—for example winter landscapes.
Vedauwoo Glen, Laramie Mountains.
The Laramie Mountains are cold and snowy in winter, but with lots of sunshine. This makes them appealing for photography outings, but also creates extreme contrast between snow and everything else, which can confuse the camera. When it compensates for bright snow, everything else is too dark. If darker areas dominate the scene, the snow turns out totally white.

I’ve tried three types of strategies for seizing the right amount of light: camera settings, post-processing, and choice of subject.

On my DSLR, I can use exposure compensation to adjust how much light is captured. A bright snowy scene seems to require +1 or even +2 to correctly expose darker areas. But sadly, the beautiful sparkly snow often gets washed out.
Camera’s exposure.
Exposure compensation of +1 revealed the aspen trunks, but made the snow-shadow pattern too bright.
Another option is to focus/meter on a darker part of the scene (button halfway down), and re-frame before shooting. But this often produces the same problematic results: dark subjects and/or washed out snow.

Unsatisfactory results can be adjusted to some degree in post-processing. In iPhoto, reducing Shadows sometimes makes dark areas more interesting without washing out the snow. A simpler alternative is conversion to monochrome—high contrast is often desirable in black-and-white photography.


Perhaps the easiest “solution” is to shoot scenes where high contrast is acceptable or even desirable—silhouettes, shadows and aspen trees for example. I like these kinds of scenes, especially in black-and-white.
High-contrast dog. Note ear as wind-sock.

Do you photograph snowy landscapes? What’s your strategy for seizing just the right amount of light?


Hayden, FV. 1871. Preliminary report of the United States Geological Survey of Wyoming and parts of contiguous territories. Washington, Govt. Print. Off. 

Hirsch, R. 2000. Seizing the light; a history of photography. McGraw-Hill.

Jackson, WH. 1870. Diary (typed transcript). William Henry Jackson Papers, New York Public Library.

Jackson, WH. 1874. Descriptive catalogue of the photographs of the United States Geological survey of the territories, for the years 1869 to 1873, inclusive. Washington, Govt. Print. Off. PDF (Biodiversity Heritage Library).

Jackson, WH, in collaboration with HR Driggs. 1929. The Pioneer Photographer; Rocky Mountain Adventures with a Camera. Yonkers-on-Hudson, NY: World Book Company.

Tissandier, G. 1877. A History and Handbook of Photography (ed. J. Thomson). NY: Scovill Manufacturing Company.


  1. Great post! I've struggled with these issues, too. But the biggest struggle for me with winter photography is simply the cold. Repeated cases of frostbitten fingers over the years makes me especially sensitive to the cold and I don't like to take off my gloves. Your images are amazing. It was fun to see the color and B&W comparisons. I need to play around with that a little more. I don't have any other recommendations beyond what you're trying already. The only additional thing I've tried at times is to slightly shift the angle of the photograph, to catch the light differently, but I'm sure you've tried that, too. Low light seems to be more of a challenge for me. And trying to photography through window glass because I don't want cold fingers. ;-)

  2. Thanks, Pat. I've not thought about shifting the angle, at least not consciously. I will keep it in mind, see what effects it can have.

    Sorry to hear about your tender hands! But your "inside" posts--through windows, of past trips etc--are always enjoyable, so hopefully you enjoy them as well.

  3. I think you meant 1835 rather than 1935 for M. LJM Daguerre's quote.

    I don't photograph snow (and my putative blog is provisionally called Some Bad Photos of Plants) but isn't the glitter off snow polarised? Presumably you could use a polarised filter to enhance that, by rotating it until you found the angle of polarisation of the glitter. If it is an exact thing you might need a tripod. The screen on the camera might be too low-resolution to show the glitter, which would make it tricky.

    Any other Pats want to comment ;)

    1. Thanks, Pat--the Plant ;-)

      I fixed the century typo. Thanks also for mentioning polarizing filter ... which I have on that lens and too often ignore, including recently. Rotating it should affect the glitter, assuming I'm pointing the right way in relation to the sun, which I don't yet understand (haven't tried). So--another issue I've largely ignored and therefore another post in my photography improvement series!