The Effect of Aperture upon Depth-of-Field

Though I teach science for a living, I have for years enjoyed taking photographs.  For much of that time, I  depended on the camera to determine the settings, leaving everything on Automatic, even when I had other options.  Finally, I got a decent DSLR camera and have begun teaching myself a bit more about photography.  I plan to create a series of posts demonstrating the effects of settings.  For the first, I want to show the power of shooting in Aperture-Priority mode (Av on a Canon camera).

When your camera is set to Aperture-Priority mode, everything is still determined for you by the camera except for the aperture.  (Thus, the name.)  Setting your aperture determines how big an opening in the lens lets in light.  Big opening = small f-stop = small (narrow) depth-of-field.  It's easier to look at this comparison of two photos shot a few seconds apart in Aperture-Priority mode with the f-stop at its smallest (left) and at its largest (right):

left: Aperture set to f1.8 (automatic setting of ISO 100 and shutter speed 1/1024 second)

right: Aperture set to f20 (automatic setting of ISO 800 and shutter speed 1/64 second)

(Click on the image to enlarge it.)  Notice that on the left, only the larger seed pods closer to me are in focus.  Everything behind is blurred.  However, in the image on the right, most of the grassed are in focus.

The effect of blurring the background, referred to as bokeh,  is commonly used in portrait photography to eliminate distracting details, keeping the person being photographed as the focus of the image.

Even a small change in aperture can have a significant impact:

left: Aperture set to f5 (automatic setting of ISO 3200 and shutter speed 1/32 second)

right: Aperture set of f1.8 (automatic setting of ISO 1250 and shutter speed 1/64 second)

Notice the blurring of the pot and window frame at the lower f-stop.

One thing to keep in mind as you reduce your f-stop/depth-of-field.  If you are using automatic focus, it may be difficult to get the items in focus that you wish:

Both photos used f1.8, but the auto-focus chose different items to focus upon.  

You can learn to control this but, for now, start by being aware of it.

Aperture-Priority mode is a good first step away from simply depending upon whatever logic is programmed into your camera---a first step in taking more control over your photographs.

Disconnected

I often carry my camera on my daily dog walk to help me get out of my head and pay attention to the physical world. From my home street, I take a public sidewalk 600 feet or so along Highway 20, a busy four-lane highway. As the sidewalk gives way to the parking lot of Harbor Freight, a ramp smooths the transition.

That ramp is largely due to the Americans with Disabilities Act (ADA, 1990) which recognized the need for public infrastructure to provide accommodations for those who would otherwise be excluded from the use of public facilities, even those privately owned. It also set standards for new construction. Changes in the law were no doubt crucial, but they were accompanied by changes in our mindset---if you ever make friends with someone in a wheelchair, you'll never see curbs the same again. The ADA greatly improved the odds of making such a friend.

This summer, a new VA clinic opened in part of what had been the K-Mart, once the anchor of the shopping center before becoming a hulking dead weight as it closed. As the east corner of the building was repurposed, the old garden center and an older and never-used-in-my-time auto shop were demolished. Newly built interior walls divided the space into offices for the VA. Near the old auto shop, a new ramp led to a side door equipped with a passcard reader. A new parking area hugged the side.

As I strolled, I pondered the disconnect that seems to dominate the U.S. currently. Can we no longer love someone we disagree with? Have we lost our ability to care for someone less fortunate than ourselves? And as I walked, the VA parking lot began to bug me.
Note how the ramp leads from the door to a crosswalk to... a curb.

To be fair to the VA, quite a few parking spots are handicap-accessible. But the curb seems to say, ""Park elsewhere, if you're disabled." It's almost arrogant, unwelcoming. And so unnecessary. Why not put a smooth transition to the crosswalk, maybe even at asphalt-level and wide enough to easily clear of snow?

I can only assume that the VA and the contractor who built the parking lot were not communicating very well. Did the contractor even think about the disabled veterans who might use the space? I bet if the contractor had a son in a wheelchair, he might have questioned the curb design.

I believe that on some level, the contractor would be ashamed if confronted with the way he constructed the curb. But if made ashamed, he'd probably resort to excuses, "There's plenty of other places to park," or "I was just doing what I was paid to do." Shaming him won't make things better. Introducing him to some of the people the VA serves, welcoming him like a family member, might.

Grading Papers

Most of my students know that I hate grading papers.  To force myself to do it in a timely fashion, I promise them that I will have their tests graded by the following Monday or they all make an A.  So far, I haven't had to do that---but I've ruined some Sunday nights.  However, occasionally grading has its interesting points.  Take a look at the female student's drawing below.  By the point in the semester when this test was given, I knew her well enough to know she wasn't trying to tweak me.

Just As I Am

On Friday night, I was invited to read an essay I wrote for the Dubuque Area Writers Guild's Gallery 2019.  Each year, the release of the Gallery marks the opening of Dubuquefest.  The Gallery is now in its 41st year.  The piece I read, Just As I Am, is about my experiences growing up Baptist in the rural South and is available [here.]

Tidying Up

I installed a bidet,
a derriere depilator,
a rectal reamer,
an anal laver. 

My wife turned it on
just to see it work,
standing up,
pressure-washing the wall.

The life-changing magic
of tidying up.
KonMari my ass!

Little War on the Prairie

My younger daughter, Tess, started college this fall at Gustavus Adolphus, just north of Mankato, Minnesota. In my mind, Mankato had nothing to distinguish it from other small Midwestern cities. About 100,000 people live in the metropolitan area, some attending Minnesota State University, the summer home until recently of the training camp for the Minnesota Vikings.

Mankato is also the location of Sibley Park, named for Minnesota’s first governor. I generally think nothing of things named for old white guys, having grown up in the South where Robert E Lee is everywhere, having caught Mardi Gras beads along Jefferson Davis Parkway in New Orleans, and while in high school having been given Senator Jesse Helms’ When Free Men Shall Stand, though I never read it.

So a park named after an old governor meant nothing.

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I love public radio—The Moth Radio Hour, Snap Judgment, and This American Life are favorites. I recently began downloading episodes to my mp3 player for listening during my morning walks with Harold, my dog. Today, I turned on Little War on the Prairie, an episode from November 23, 2012. John Biewen, who tells the story, grew up in Mankato, ignorant during his youth of the events of the war between the Dakota and European settlers that took place in 1862. The podcast is his story of educating himself, and it worth your time.

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The Dakota War ended with a mass hanging of 38 Dakota men on December 26, 1862. It was the largest mass execution in U.S. history.

Currently, on the site of the execution is a public library, across Riverfront Drive from the Minnesota River, upon whose banks the 38 bodies were buried in the sand. During the night, the bodies were dug up for use as medical cadavers, including by William Worral Mayo, whose name adorns Minnesota’s famed Mayo Clinic. Mayo dissected Stands on Clouds, then varnished the skeleton and kept it in his home office for his sons to study.

A less-than-two-mile walk along the river from the execution site brings current visitors to Sibley Park. Henry H. Sibley, first governor, was picked by his successor as colonel of the state militia, with the charge of suppressing a Dakota uprising. After leading in multiple battles and capturing more than 1000 Dakota, Sibley appointed the military commission that condemned 303 Dakota men to be hanged. Only the personal evaluations of the cases by President Lincoln reduced the number to 38. A week before the hangings, Sibley wrote the Assistant Secretary of the Interior,

[I]t should be borne in mind that the Military Commission appointed by me were instructed only to satisfy themselves of the voluntary participation of the individual on trial, in the murders or massacres committed, either by voluntary participation of the individual on trial, in the murders or massacres committed, either by his voluntary concession or by other evidence and then to proceed no further. The degree of guilt was not one of the objects to be attained, and indeed it would have been impossible to devote as much time in eliciting details in each of so many hundred cases, as would have been required while the expedition was in the field. Every man who was condemned was sufficiently proven to be a voluntary participant, and no doubt exists in my mind that at least seven-eighths of those sentenced to be hung have been guilty of the most flagrant outrages and many of them concerned in the violation of white women and the murder of children. (Source [here.])

To a Native American, seeing Sibley Park must be similar to an African American driving by Lee Circle. (See [here] and [here.]) The turmoil resulting from the removal of multiple Civil War monuments continues to roil the South as I write this. Similarly, most monuments to the Dakota War memorialize the white soldiers and settlers. (See [here.]). At the end of the Dakota Wars, all Dakota were banished from Minnesota. Few remain to object to a park named for a former enemy.

But a few Dakota have returned. In the current times of intense anger, they are guides to our better selves. Across the road from the public library—the massacre site—Reconciliation Park opened in 1997, with a theme developed by the Dakota of Forgive Everyone Everything.

But forgiving doesn’t mean forgetting.

The philosopher George Santayana said, “Those who cannot remember the past are condemned to repeat it.” I first encountered the quotation on a display as I entered Dachau Concentration Camp near Munich, Germany.

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