Print: Go With the Flow

Go With the Flow

An Alaskan brown bear meditates as the river flows by during this sunny and crisp fall day in Katmai National Park, Alaska.

A Pause to Reflect on Fall

Fall comes early to Katmai National Park. This is the time when this wilderness landscape shows its colors before the white blanket of winter arrives. Slopes of tundra light up the higher elevations with a quilt of reds, purples, greens, and yellows. Cranberries, blueberries, crowberries, and watermelon berries abound everywhere. It is a time of abundance.

Brown bears travel far across this wilderness to the salmon-choked streams. By the time fall arrives most salmon have spawned and died in these spawning areas. Soon the bears will hike up to high elevations and dig their hibernation dens. Deep snow high up on the mountains insulates their underground dens from the cold Alaska winter.

The bear in this photo was relaxed as I watched in him in the river. In between meals of salmon he would take long pauses as if he was daydreaming. Salmon were easy to come by, and his thick fur coat covered the layers of body fat he developed over the summer.

In order to capture his pause, where he seems to be meditating, I used a slow shutter speed to blur the flow of the river. Perhaps he was savoring this beautiful fall afternoon before hibernating the long winter.

The Story Behind the Photograph

Katmai was heavenly when I arrived this September. Colorful foliage completely changed the landscape that I had explored earlier in June and July. As soon as the float planned dropped me off at Brooks Camp I hiked up Dumpling Mountain to set up my tent above all the activity way below me. It was quiet and peaceful in my lofty camp up on the tundra. Cranberry, blueberry, crowberry, and watermelon berry plants were all around me, offering up their tasty fall fruit.

The Science Behind the Photograph

There are some interesting scientific questions that arise when looking at this photograph. How did the camera freeze action on the bear while letting the water in the river blur? Why are the colors of the water so rich? Why is the fastest moving water white, and the waves in the rapids blue-green?

I was able to freeze the motion of the bear while letting the water blur through sheer luck! Well, actually using a technique similar to a method in astrophotography called “lucky imaging“.

The bear was moving, somewhat randomly, and the water was also moving. The water and bear motions were on different time scales and uncorrelated. The relaxed bear moved relatively slowly compared to the rushing water. More importantly, the bear’s motion varied from near zero, when he was daydreaming, to a faster motion, when he chased after a salmon. The river’s motion was more constant and fast.

Using a slow shutter speed (1/10 sec) I took many images, hundreds of them, and then looked for ones where I was lucky and the bear held still while the camera shutter was open. Although a tenth of a second may seem like a short time to us, the rushing water moves a lot during this time. During this short time window, the bear can also blink, flinch, move his head, and also become blurred during the exposure.

Understanding why the colors of the water are so rich is a bit more difficult.

The color of the water in the river that we see depends a lot on the light in the environment of the river. Colors from the forest, shoreline, and sky reflect from the water surface to our eye. In this photograph, you can see the browns and yellows of the distant shore reflected from the smoother areas of the river’s surface.

In the more turbulent parts of the river, we see white. The turbulent water, in the fastest rapids and waterfalls, is filled with many spherical air bubbles. These air bubbles vary greatly from less than the wavelength of light to several millimeters in size.

Each bubble scatters light in different directions and colors. The ensemble of these many bubbles scattering light sum to white light. The same effect occurs when any colored material is ground into a fine powder, we see the powder as white, even when the underlying material has a definite color. This is also the reason why clouds in the sky appear white, except clouds are full of tiny water droplets, instead of air bubbles.

The wave surfaces in the rapids are a blue-green color. When we look through a glass of water it is clear. When we look through a thicker volume of water we see a blue-green tint. You can see this when comparing the color of the deeper end of a swimming pool to the shallower end. Water molecules absorb longer wavelengths (red and orange) more than the shorter wavelengths (purple and blue). The spectrum of sunlight is stronger in blue than purple, and the sensitivity of our vision is highest in the green part of the spectrum. When we look through the thicker parts of the water waves we see blue-green due to the combination of these effects (water absorbs reds more than blues, the spectrum of sunlight has more blue than purple, and our eyes are most sensitive to green).

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Go With the Flow

(30 x 45 in print shown here for scale)

Go With the Flow

Katmai National Park & Preserve, Alaska, September 2018

Go With the Flow

A Pause to Reflect on Fall

The Story Behind the Photograph

The Science Behind the Photograph

Limited Edition Prints

Go With the Flow