What is the Decisive Moment

The term was coined by Henri Cartier-Bresson, whose definition of photography was "the simultaneous recognition in a fraction of a second of the significance of an event, as well as the precise organization of forms that give that event its proper expression". For HCB, photography was synonymous with capturing the decisive moment.

My interpretation of the decisive moment is that it's a local maximum of coherence: a picture taken a little before, or a little after, or aimed a little to the left, or a little to the right wouldn't be as good, and you can tell that from looking at it.

A distinguishing characteristic of Henri Cartier-Bresson's photographs is that they look like drawings. When you draw something, you think about what you draw -- you consciously arrange and separate shapes; you wouldn't place a chandelier right on the top of someone's head unless you meant it. Unfortunately, most people don't see it this way; they live in a 3D world and they don't recognize the fact that a photograph is inherently two-dimensional and a result of projection; their pictures, a pile of people and things, require the viewer to consciously separate the objects by reconstructing the 3D scene in their head.

Now let's talk about form. Our visual system recognizes form based purely on value, or intensity. That's why black-and-white photography is so fundamental. If you don't believe me, take it from Van Gogh, the master of color: "drawing is the root of everything". Drawing, which is monochrome.

So we have two components: "significance in a fraction of a second" and "precise organization of forms". Without any pretense at high art, and as means of illustration, let's try to put these things together.


I'm walking in New York City at night. I see something I like.

Why does it draw my attention? I like the tree and its shadow, the window outlines and the lights.


I compose the frame more carefully and wait for some people to pass by. I choose three, because they rhyme with the lights.

However, I don't like the corner of the street, visible on the left, the extra light reflected in the window is annoying, and there is not enough intensity difference between the lady on the left and the window. Unfortunately, it's a cold night, so not a lot of people are passing by.


I shift around to see if I can find something more interesting in terms of composition.

I like the shadow of the tree branches on the wall and the window-door relationship. However, there is no decisive moment here, because an hour later, this scene will look exactly the same.


I wait for someone to walk by. When do I press the shutter? Certainly not when they're level with the window, because the window consists of lines that I don't want to break. If they're wearing something light, I might choose the moment of time when they are passing the door, which is very dark.

The problem with this picture is the lack of significance of the moment -- it's not a local maximum of coherence. Any other person would do just as well. Fortunately, waiting always increases the chance of coincidence.


This is my decisive moment. The bag rhymes with the lights -- in fact its shape, framed by the legs, is that of a cone of light. If I pressed the shutter a little before or a little after, the "organization of forms" would shift, and the effect would be gone. You can tell this from looking at the picture. Therefore, we have captured a decisive moment.

References (links lead to Amazon.com)

Vincent Van Gogh: The Drawings
Vision and Art: The Biology of Seeing
Henri Cartier-Bresson: The Man, the Image & the World: A Retrospective
Henri Cartier-Bresson and the Artless Art

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© 2003-2006 Alexei Lebedev