Bokeh. ¿Por Que?

“Bokeh” from the Japanese word boke meaning to blur or to “fuzz something” is a technique used by visual artists to blur the background or foreground (or both) of a scene to move the eyes of the viewer towards the intended subject. Bokeh makes a scene look more “real” and less Flatland, though this is not always the desired effect when taking pictures.

Portraits like to have bokeh unless you’re taking a picture with a nondescript background like a white or black backdrop in a studio. Sometimes, bokeh is used even with a backdrop to simulate a scene if the backdrop has some sort of image on it, like a forest or a European Cathedral or even The Pope in the Pope-mobile! Okeh, maybe not that last one. This is why portraits that are taken with a cheap point-and-shoot camera usually don’t look as good as a more expensive point-and-shoot where there’s usually a “portrait mode” or allows control of the aperture. Aperture. What does that have to do with bokeh? Okeh, I’ll tell you. But, first, let’s talk about “exposure”.

Exposure is everything, then comes focus. Odd that I would say that since a blurry image does nobody any good unless you’re the “artsy” kind <smile>. Anyway, exposure is a balancing act. It is comprised of three variables: aperture (there’s that word again!), shutter speed and ISO (film sensitivity). Okeh, I lied. Exposure comprises of four things: luminance being the fourth (or is it the first?). The reason I said three is because you can only set the first three variables in the camera. Luminance is how your scene is lit. Yes, you can use controlled lighting, but for the sake of argument, we’ll keep the lighting au naturel. So exposure is really “how much light” gets into the camera.

Aperture is how wide the, um, aperture of the lens is opened (okeh, call it the iris). The wider the aperture, the more light comes in. Makes sense huh? Shutter speed is the speed of the, um, shutter. The slower it is, the longer the shutter stays opened, and the more light comes in. Make sense? ISO (acronym for International Organization of Standarization (I know. Silly.)) or film speed is the sensitivity of the film to light. For digital cameras, the sensor replaces the film (like, duh).

So let’s say that we are out and about with our cameras with an 85mm lens on it on a sunny day taking pictures of people, dogs and flowers. We set our cameras to “Av” mode or aperture priority mode, then set the ISO to something like, say, 200 since we don’t need too much sensitivity. We then open up the aperture as wide as possible. In my case, f/1.2 (oh, the lower the number, the wider the aperture). My camera tells me that the shutter speed should be 1/640 of a second. We take the picture of the purdy lady under the tree and we get…

Carline / Canon 5D II, Canon 85mm f/1.2L, f/1.2, shutter 1/640, ISO 200

Pretty, huh? So what happened here? Welp, let’s break it down.

The first thing you’ll notice is the background and how blurred it is making it less distracting. This is called a shallow depth of field. But why is Carline’s, uh, decollete out of focus if it’s not in the background? Well, in a way it is. Notice that her right arm, nose and eyes are in focus. That’s because they are closer to the camera and on the plane of focus. This effect was produced by the wide aperture of the lens. If I had closed the aperture one or two “stops” (more on this later), everything about her would have been in focus while still having the background blurred. So in the above photo, we have a very shallow depth of field (DOF). This means that the plane of focus (or focal plane, DOF, etc) is very thin. Imagine a piece of glass touching Carline’s nose (which is probably where I focused). The focal plane is the thickness of the glass. In this case, I was standing about 10 feet from her, my lens was 85mm and the aperture was f/1.2. According to my DOF calculator (“There’s an App for that!”) the “glass thickness” would be about 3 inches: 1.68in in front of the focus and 1.2 behind the focus. This means, anything 1.68 inches from her nose to anything 1.2 inches behind her nose will be in focus. Everything else will be blurred.

You’re probably wondering why I went through all this explanation of exposure just to tell you that, essentially, aperture controls bokeh. Well, because there’s some important theory that needs to be discussed. Let’s go back to the photograph.

I mentioned that my camera was set to aperture priority. In other words, I set the aperture and the camera calculates the shutter speed based on the other three variables that comprise the exposure. Also, remember that exposure is a balancing act, so if I stop down the lens (meaning make the aperture smaller), the camera will increase the shutter speed (making it slower) to let in the same amount of light as with the previous aperture setting. The problem here is if I close the aperture too much, the shutter speed will probably be too slow for me to take a sharp picture since I run the risk of the subject moving or camera shake. This is why you would use flash in low light situations: you want to freeze the scene (this, by no means, is the only reason for flash; more on flash later). An interesting thing happens the more you stop down a lens: the depth of field increases. In other words, your background, in this case, gets more and more into focus. Here’s an example

Carline / Canon 5D II, Canon 85mm f/1.2L, f/16, shutter 1/15, ISO 400

In this shot, Carline is photographed with an aperture setting of f/16. As you can see, the background is in fairly sharp focus. The photograph could have been take with a point-and-shoot in fully automatic mode. The photo is quite uninteresting (though the subject is not <smile>). We can fix this by opening up the aperture a bit.

Carline / Canon 5D II, Canon 85mm f/1.2L, f/1.8, shutter 1/1250, ISO 400

Now THIS looks more interesting! There is more to bokeh than just opening up the lens aperture. You also have to take into consideration the focal length of the lens, the distance to the subject, the alignment of the stars, etc. But, generally, aperture.

“Ok, so how does this relate to exposure?” Well, it doesn’t, but because people tend to be curious, one runs the risk of the following line of thinking:

  • Exposure is a balancing act
  • Proper exposure of a scene will always incur the same light coming into the camera.
  • So, the smaller the aperture, the slower the shutter speed needs to be to get the same light.
  • Changing the aperture causes focal planes to shrink and grow. And since there is a relationship with the shutter speed….
  • Changing the shutter speed should also affect the focal plane.

Um, no. That’s not the case, so erase it from you mind. But, hey, at least you learned something about exposure! To get the true how’s and why’s of bokeh, you have to turn your attention on lens technology and such. A topic that I will not discuss here (actually, I’m just taking it for granted, but if you want to boggle your mind a bit, look up “bokeh” in Wikipedia).

So next time you take a portrait of something, “bokeh it up” a bit to make it interesting. You may get really cool results. Here’s an example

Old Man Facing East / Canon 5D II, Canon 85mm f/1.2L, f/1.6, shutter 1/1250, ISO 400

Notice how the picture is almost 3D. You can almost reach in and touch the man (not that you’d want to; he looks kinda grumpy). So, if bokeh is sooooo cool, why would you NOT use it? Well, my questionable friend, there are MANY reason not to use the bokeh technique. <pause> Wait, I’m thinking…..<pause> Um, “many”.

Architectural photography or when photographing interiors where you need to show everything in the room or space, like this next example

Hallway (Staten Island, NY) / Canon 5D II, Canon 24-105mm f/4L IS @ 67mm, f/22, shutter 1/6, ISO 6400

For this shot, to get all the bricks in focus, I needed to close the aperture to f/22. I still have a sense of depth thanks to perspective. So the rule of thumb is to use bokeh to single out your subject from a scene. To bring attention to your subject.