Archive for March, 2011

Capturing movement

Thursday, March 31st, 2011
Capturing movement

After a post of an image on Facebook of the flowing Virgin River in Zion National Park, I thought it would be helpful to post a blog on capturing movement.

Photography is often about rendering a scene using a camera in a way that reflects how our eyes perceived it.  Our eyes view action as a fluid process, not as a freeze frame (that is, unless we are constantly blinking while viewing movement).  So while sometimes for documentary purposes it is essentially to freeze a moment in time, like with sports action photography, sometimes it is preferable to capture that movement in a way that we perceive it, or, to put another way, in a more “artistic” way.

Capturing movement is a mere matter of using a slow enough shutter speed to show movement in your subject.  How slow depends on the subject.  For the rotors on a helicopter, for example, movement will show nicely at 1/125 of a second shutter speed.  But water, on the other hand, may take as slow as 1/15 of a second before the blur of movement begins to show.

There are two aspects of technique to consider when capturing movement.  The first is how to get that slower shutter speed.  Shutter speed is determined by three factors: ISO selection, aperture setting, and available light.  So, a good starting point in sunlight for your ISO setting is the lowest you can go; typically 100 or 200.  Next, you want to set your aperture for as narrow as it can go, typically f/22.  The third factor, available sunlight, will likely affect the first two.  For capturing water falls or streams, for example, it is preferred to photograph in the shade or under overcast conditions.  This allows you to create the lowest shutter speeds possible.  But if it is sunny, you cannot get down to a shutter speed of 1/2 second, even at ISO 100 and f/22, without some additional help.  One way to reduce further the shutter speed is to add a polarizing filter, which takes away up to an additional two stops of light.  Another way is to add a neutral density filter; not a graduated neutral density filter, but a neutral density filter that covers the entire face of the lens.  Like with a GND, you can acquire neutral density filters at one, two and three stop intervals.  How slow is too slow depends on the look you want.  If you want some detail in your water, for example, then one second is probably enough.  But if you have the right lighting conditions and want more of a foggy, diffuse look, then up to 15 or 30 seconds will produce the desired result.

The second aspect of technique to consider is where you want the movement to be: on the subject or the background.  For movement on the subject, the camera should be stationary – mounted on a camera.  Otherwise, you will have undesired camera movement.  This will allow you to have movement in your subject, such as water or fireworks, while allowing the rest of the scene to remain in sharp focus.  But, if you want your subject to be in focus but have the movement in the background, then you will need to pan.  A classic example of this technique is when the subject is moving parallel to you, like animals running from left to right or a flock of birds flying from one location to another.  Here, you do not need to slow down the shutter as much to show movement – often a shutter speed of 1/60 will suffice.  But there is a fourth factor that will affect what shutter speed you use in addition to the three mentioned in the previous paragraph: focal length of your lens.  The longer the focal length, the higher the shutter speed you can use and still get movement.  Much of the process of selecting the right shutter speed for the panning technique is trial and error: how much movement is too much, how you are able to obtain sharp focus where needed, etc.

Here are some examples that employ both techniques.

Shooting (for) the Moon

Monday, March 21st, 2011
Shooting (for) the Moon

Knowing how to shoot the moon requires a solid understanding of how exposures work, or more specifically, knowing the limitations of how cameras see light.  You cannot photograph the moon in a nighttime landscape and expect a good result if you are exposing for a city skyline, for example.  Why is that?  Well, think of the light source for the moon – the sun.  The moon is simply a large reflector with an ash gray surface, reflecting the sun’s light back at us at an intensity comparable to midday light.  In fact, you can use the “Sunny f/16 Rule” to manually set the exposure for a full moon at its brightest.  Understanding how truly bright the moon is and how quickly it moves across the sky are key to knowing when and how to photograph it with a broader landscape.

When is the best time to photograph the moon with the landscape?  The absolute best time is when you can set a single exposure that both correctly exposes for the moon and the landscape.  That means, the best time is when there is some amount of daylight available, usually at the margins of the day.  I have found the best time is to capture a moonrise at or near sunset or a moonset at or near sunrise.  At those times, the exposures necessary to capture the moon without blowing it out (losing the detail in its surface) are about the same as those needed to capture the landscape.  How do you know when this timing occurs?  I regularly use the U.S. Naval Observatory “Complete Sun and Moon Data” web page for this information.  There, you can enter a date and location, by either city name or latitude and longitude, and get complete information as to sunrise and sunset, moonrise and moonset, twilight, and the phase of the moon.  This is also useful for aurora photography, because you want to know if the moon is going to be too bright to capture the aurora.

Now, if it turns out that the exposure time needed for the moon is slightly faster that what you need for your landscape, then simply use a graduated neutral density filter to darken the moon just enough to balance your exposure.

But what about those nighttime exposures?  First, you have to decide whether it is important to capture the detail in the surface of the moon.  If it is not important, and you don’t mind (maybe even want) the moon to be a large glowing orb in the sky, then simply expose for your landscape and click that shutter release button.

But, if you want the moon to be correctly exposed and you want your landscape to be correctly exposed, then you have to take two exposures – one for the moon and one for the landscape – and then merge the two together in Photoshop.  When you do this, however, you will notice that the moon looks really small, particularly if you are shooting a wide angle lens or a panoramic.  The only way to make the moon look big is to really zoom in, typically with a 500mm lens.  But you run the risk of creating a VERY obvious composite if you use that 500mm moon capture and merge it with your landscape that was captured with a 70-200 lens, or even worse, a 500mm moon with a 24mm landscape.  The moon ends up looking unnaturally and ridiculously large.  To see an example, check out the panel of three panoramas below: one with the same exposure for moon and city, one with separate exposures, and one with separate exposures AND different lenses.  Of course, whether it is still “appropriate” to use the composite with the unusually large moon depends on whether you are trying to depict things as they naturally are or as they are perceived.  For the composite example below, it was our 18-year “super” moon, where it is perceived as much larger than a usual full moon due to the closer proximity of the moon.

The other important thing to remember is that the moon is moving faster across the sky than you realize.  This will affect how your exposure looks if you are using a wide angle lens and you are using a longer exposure to capture a dark landscape.  During that exposure, the moon is moving, and burning its light across the sky in your composition.  It will also affect the framing and composition of your image if you are using a long lens, like a 500mm.  If you have a tight crop, the moon will move quickly out of your frame.  To illustrate, check out my multiple exposure below of the lunar eclipse that occurred during the winter solstice last year.  Each image of the moon represents about a 45 second time lapse.

Iditarod, a Great Alaska Tradition

Monday, March 7th, 2011
Iditarod, a Great Alaska Tradition

DeeDee Jonrowe, one of the more well-known dog mushers in Alaska, not only because she has had many successful runs but is a cancer survivor, said during this weekend’s Iditarod start that the Iditarod is a celebration of Alaskan culture.  Dog mushing is certainly not unique to Alaska, nor is professional dog mushing racing, but there is something special about the Iditarod and its place in the Alaskan worldview.

Before living in Alaska, I spent nine years in Minnesota, where I attended college and graduate school.  In between the two schools, I spent a couple of years up north working as a canoe guide in the Boundary Waters Canoe Area Wilderness.  It was there that I began to learn about dog mushing because of the John Beargrease Sled Dog Marathon.  But I never made it down to Duluth (I was living in Grand Marais) to see any part of the race.  I never got the sense that it was the sort of thing that people traveled long distances to see, that it had more of a regional impact.

But the Iditarod is something else entirely.  People come from all over the world to Anchorage just to see the ceremonial start, and stay to see the official start in Willow the next day.  Some even stay long enough to go to Nome – NOME – to see the first finishers come in to town.

There are so many things that make Iditarod not only a great Alaskan tradition, but one of the many things that makes Anchorage a special place to live.  The entire downtown atmosphere during the day of the ceremonial start (always the first Saturday in March) is an extremely festive atmosphere, mixed with the excitement of being in the midst of some of the biggest stars in the wild sport of dog mushing.  Prior to the official start, members of the public are free to interact with the mushers and their dogs, ask questions, pose for pictures, and simply be part of the excitement of getting ready for heading out on the trail.  Once the first team leaves the starting mark, members of the public can still line the streets, holding the Anchorage Daily News Iditarod guide that identifies each musher, allowing people to cheer on each musher by name.

Given the very public nature of the Iditarod, there are always other things going on that take advantage of the publicity.  Usually, someone from the Alaska congressional delegation and/or the governor are there to perform some official function.  In 2008, Governor Sarah Palin was on hand to sign into law a bill that commemorates the first Saturday of March as Susan Butcher Day, named after a four-time winning musher who died of cancer in 2006.  There is always someone waving a protest sign, promoting some issue of local concern.  And frequently some corporation is passing out swag to promote product recognition, like when Target first came to Alaska and had a crew there in force.

But the ceremonial start of the Iditarod is just one part of the festive atmosphere in Anchorage.  The dog teams mush down through town, along the Chester Creek trail, through Far North Bicentennial Park, and over to the Campbell Creek airstrip on BLM land in the heart of the city.  All along the way, fans line up to look for their favorite mushers and to cheer teams as they tour through town.  I can think of no other major sporting event where people of the public have such access to the event participants.  It is an openness and accessibility that is rather fitting for Alaska, and Anchorage, where the land is open and people are free to pursue what they enjoy doing in the outdoors.

To follow the progress of this year’s Iditarod, visit the official Iditarod website.