The poster has on it the famous photo of a South Vietnamese general shooting a prisoner in the head. I don’t read Danish, so I could not determine why the poster had that image. It is a hard one to forget.

That photo was one of two photos that helped end the Vietnam War. The other was of a Vietnamese girl running naked after a napalm attack.

Despite being seriously burned by the firebomb, the girl survived. She later moved to Canada and became a motivational speaker. She still has extensive burn scars.

More recent photographs have also had great impact.

Did you see the 1993 photo of the starving African child with a vulture waiting a few steps away? I donate money to starving children in part because of that image.

Remember the image of the dead refugee boy who washed up on the south of Europe a few years ago?  

After the publication of that photo, European countries opened their borders to refugees, at least for a while.

Not all powerful photos show tragedies, though.

Think of the famous still image, from video, of a man standing on the moon.

That image shows the intellectual and technological potential of humans.

The image and what it represents helped prompt a number of young people to become scientists.

I have never taken an iconic photograph, but I did once get a photograph published.

An article I wrote was accepted for publication by a scientific journal. That happy event has happened to me many times.

This was the only time though that I was asked to provide the journal with a photo related to the study.

In this case the study showed the risk of a halo effect when instructors mark the work of a student they know.

My photo idea was for an image of a student in class looking as if he or she adored the instructor.

Because none of my students ever look adoringly at me, I staged the scene with a research assistant.

I then had my daughter add a halo to the photo of the “student.” The result was outstanding, if I do say so myself.

What is the best photograph you have ever taken? What story does it tell? When was the last time you showed it to someone?

John Malouff is an Associate Professor at the School of Behavioural, Cognitive and Social Sciences, University of New England.