A while ago we started our new educational series covering the basic terms of photography. The letter ‘A’ covered the term ‘Aperture’, and today we continue with the letter ‘B’. Our subject for ‘B’ is ‘Bokeh’–a term that is inevitable these days. As a beginner in photography, you will no doubt stumble upon it at some point or another. And you will find many people raving about it, and others railing against it. But what is ‘bokeh’, really? Head past the break to find out.
Let’s start with the origins and original meaning of the word ‘bokeh’ itself. ‘Bokeh’ derives from the Japanese term ‘boke-aji’ (pronounced /boh-keh-ah-jee/ written ボケ味 in Japanese), which refers to the quality of the blurring of out-of-focus areas in a photograph. As established in our post on the letter ‘A’ mentioned above, the longer a lens’ focal length, the wider its aperture and the closer you focus, the more the background will be blurred away. The term ‘bokeh’ refers to the aesthetic quality of that out-of-focus blur. The ‘h’ in its Latin spelling has probably been added so as to indicate that the final ‘e’ is actually pronounced–it is /BOH-keh/, not /bowk/ (compare Wiktionary‘s entry for the term).
So, literally, ‘bokeh’ means ‘blur quality’. When you’re perusing forums, opinion pieces or educational articles on the internet, you will find people mentioning things like ‘creamy bokeh’, ‘gentle bokeh’, ‘harsh bokeh’ or ‘busy bokeh’. Especially when the optical performance of a lens is being discussed, one major focus will be on its bokeh, whether it is ‘creamy’ or ‘busy’, ‘gentle’ or ‘harsh’, ‘smooth’ or ‘rough’. But who defines what is aesthetically pleasing and what isn’t? And what makes the bokeh of different lenses be different?
First off, let’s take a look at some examples of bokeh. I will not comment on them right away, but rather let you make up your own thoughts about them before I go on to assess what we’re seeing in each picture.
Above, we’ve seen six examples of bokeh in pictures. In each picture, there is a foreground motif and a background that is more or less blurred away, sometimes with highlights that take on a circular shape due to the form of the lens’ aperture. In each case, however, the background blur looks different–has a different ‘boke-aji’. But what exactly are we seeing in the pictures above?
Example 1 has been taken with a Voigtländer Nokton 35mm f/1.4 lens for Leica M-mount. The Nokton is a classic lens design that is imitating the original Leica 35mm f/1.4 Summilux-M lens. As is typical for fast wide-angle lenses such as the original Summilux or the Nokton, the bokeh appears ‘busy’ in areas of high contrast. ‘Busy’ in this case refers to the fact that the blurring isn’t smooth at all, but rather characterized by obvious, bright outlines around the contrast edges of the defocused areas. This appears unpleasing and is not considered ideal, because it attracts the viewer’s attention instead of focusing it on the subject.
This picture shows a scenario that brings most lenses to their limits: foliage against a bright background. The high contrast between the foliage and the sky in the background is the ultimate test for a lens’ bokeh, and only the most elaborate designs will show soft and gentle out-of-focus blur under such conditions.
Example 2 was shot with a Pentax 25mm f/1.4 CCTV lens adapted to an Olympus E-P1 camera. The lens was originally designed for surveillance cameras, and was not originally intended to be used for still photography. In this picture, there is a noticeable ‘swirl’ in the out-of-focus area. It seems that the bokeh is circling around the subject. This ‘swirly’ bokeh is often found in older lens designs and with wider focal lengths. In this case, it is exaggerated by the fact that the image projected by the lens does not cover the whole sensor of the E-P1 camera, causing vignetting (i.e. dark edges), which further pronounces the swirl effect.
Nowadays, swirly bokeh is not desired and lens designs strive to achieve a more even background blur. However, many find it pleasing and specifically use lenses that exhibit it.
Example 3 is a prime example of smooth and gentle out-of-focus blurring that helps focusing the view on the subject–the little flower in this case. It was taken with a tele lens, a Tokina 135mm f/2.8, with the aperture wide open. Due to the long focal length and wide aperture of that lens, the background is blurred away strongly, to the point where you’re unable to make out anything specific except for slight changes in hue and brightness. This kind of bokeh is most desirable in order to isolate a subject, because it does not attract the viewer’s attention. Also, this is the kind of bokeh most people describe as ‘smooth’, and that most people expect from their lenses under all circumstances.
Example 4 was taken with a lens with a shorter focal length, namely an SLR Magic 35mm T1.4 lens, which is untypical for portraits. As I have shown for example 3, a longer lens will cause greater and often more pleasing blur than a shorter lens. In this case, however, the quality of the bokeh is what many would describe as ‘creamy’. It is smooth and gentle without the harsh outlines we saw in example 1, but not as strongly blurred as in example 3–you can still make out shapes and details. Yet, the blur is strong enough to isolate the subject from the background and direct the viewer’s attention to it.
Example 5 is the absolute opposite of example 4: the bokeh is harsh and busy, and overall distracts the viewer more than it helps them focus on the subject. However, from a compositional point of view, the busy highlight bokeh to the right provides the necessary balance for the head on the left. For this picture I was also using an older lens, a Revuenon 50mm f/1.4 in Pentax K-mount. Especially at wide apertures, the inherent optical flaws of a lens design become apparent. Stopped down to f/2 or f/2.8 the bokeh of this lens becomes much smoother, that is without the harsh outlines around the contrast areas (called ‘donut rings’ when the defocused highlights are circular).
Example 6 demonstrates the use of out-of-focus blur just for the sake of achieving an aesthetic effect. In this case, I deliberately defocused the lights in the background so that they would appear as colored circles in the picture. Defocusing bright lights in a dark enviroment–e.g. street lights at night–also provides a challenge to most lenses and will show off the amount of consideration that the lens’ designers put into its out-of-focus rendering. The more a lens is optimized for bokeh, the more even the defocused highlights will appear, without the ‘donut rings’ we saw in examples 1 and 5.
With discussing the six sample images I provided, we not only took a look at different types of bokeh, but also ascertained what the purpose of bokeh is. First and foremost, it is a means of isolating a subject, of directing the viewer’s attention to the object in the foreground. However, bokeh can also be used creatively or as a means of composition, such as in examples 5 and 6. In the end, bokeh is just another category of a lens’ inherent optical qualities. Some lenses are optimized to provide smooth and gentle bokeh, others aren’t.
As a rule of thumb, the longer a lens’ focal length and the wider its aperture, the stronger the background will be blurred. Also, shorter focal lengths tend to cause busier bokeh than longer focal lengths, and in general lenses featuring aspherical optical elements provide smoother bokeh than lenses with solely spherical elements.
Bokeh isn’t everything, though. While it is pretty easy to create an interesting image by simply defocusing the background and isolating the subject, it is all the more difficult to maximize depth-of-field (so that both foreground and background are rendered sharply) and use composition as a means of creating an image worthwhile to look at. So while there is definitely a reason for some people’s raving about bokeh, there is also a very good reason why others demonize it so passionately.
For more information on bokeh, I recommend the corresponding Wikipedia article as a starting point.
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