Following up on Michele's recommendation to revisit some of our earlier assignments, I'd like to revisit the "Bokeh" assignment. We originally covered this assignment back in August of 2009 in
this thread. As I mentioned in the original thread, bokeh (pronounced bo-keh, and derived from the Japanese word boke, meaning fuzziness or blur) is a photographic term referring to the aesthetic quality of the out-of-focus areas of an image. Out-of-focus areas in some images can appear "jarring" or distracting enough to steal the viewer's attention from the primary subject, while other images have more smoothly defocused areas that contribute to the overall design of the image. Bokeh can refer to lens characteristics and the way a lens "draws" an image, or more specifically, to the characteristics of the out-of-focus areas of a particular image. Lens designs have continued to improve over the years, and as photographers become more descriminating, lens designers are trying to design their lenses to provide pleasing bokeh (as well as a sharply rendered primary subject). A lens with "good" bokeh creates smooth, aesthetically pleasing out-of-focus backgrounds and produces an image where the in-focus subjects "pop" or stand out in sharp contrast to the softly blurred background.
Bokeh is one area where art (the aesthetic appeal of an image) and technique definitely overlap; however, this requires the photographer to pay attention to both the in-focus
and out-of-focus areas of an image. (Beginning photographers often pay attention to the sharpness of the primary subject, but don't spend enough time evaluating the out-of-focus areas of their images, or adjusting their settings to get pleasing bokeh.) If you want to improve the aesthetic appeal of your images, it's worth spending time looking through images that you like and paying attention to how both the in-focus and out-of-focus areas are rendered in those images. It's a good bet that very few (if any) of the images that appeal to you will have "jarring" or ugly/distracting out-of-focus areas.
So exactly how can we adjust our techniques to produce more pleasing bokeh? First, you should recognize that your lens choice can have a major impact on the bokeh of the images. Lens designers concerned with producing pleasing bokeh will use more aperture blades or design the blades so that they produce a smoothly curved round opening (approximating a circle) when stopped down (adjusted from their wide open positions). It might be worth checking the description of your lens to see if any of those characteristics (more aperture blades or rounded aperture blades) are specified, and then choosing a lens appropriately when bokeh is a concern. Second, lenses with larger available apertures provide the flexibility to shoot with more "wide open" apertures, which can often contribute to the smooth, creamy out-of-focus areas that most people find more appealing. Many lenses will produce relatively pleasing bokeh when shot wide open, but less pleasing bokeh when stopped down.
Since focal length (magnification of a lens) will also affect depth of field (with greater magnification resulting in less depth of field), choosing a longer focal length lens can result in smoother out-of-focus areas. Be careful here though, since some mid-range telephoto lenses are notorious for "bad bokeh." (See the previous Bokeh assignment to read more about some characteristics of "bad" bokeh, including "ni-sen," which is characterized by double-line streaks when rendering out of focus objects (typically from "over-correction" of spherical aberrations in the out-of-focus regions).)
There is obviously a correlation between the shallower depth of field associated with longer focal length lenses, and the way this narrower depth of field translates into a more pronounced transition from in-focus to softly out-if-focus areas. This is important because it is the areas in an image that are "in-between focus," i.e not quite in-focus, but not softly out-of-focus either, that can be the most distracting, especially if these "in-between focus" areas are high contrast, or accentuated by the double-vision ("ni-sen") affect caused by some lenses. Since longer focal length lenses will have a narrower range of distances that fall within this "in-between" focus range, use of these lenses can make it easier for the photographer to control the rendition of out-of-focus areas.
We can control what areas of our image are in-focus or out-of-focus (and eliminate the "in-between" focus) by controlling the depth of field in relation to the primary subject and the foreground/background areas of the image. We can narrow the depth of field by using a longer focal length lens or getting closer to the primary subject (more magnification) or by using a larger aperture. Remember that whether or not your background will be in focus will be determined by the
relative distance between your primary subject and the background. For example, if you are photographing a subject that is about 3 meters away with a mid-telephoto lens, and your background is between 1 and 3 meters behind your primary subject, it will almost certainly fall into the "in-between focus" area and be a distraction in your image (unless you are shooting with a very large aperture). If however, you move closer to your primary subject (to within one meter or so), then the closer focusing distance will result in a much narrower depth of field and make it relatively easy to render the background softly out of focus. When composing or designing your image, it is important to pay attention to the relative separation between your primary subject and the background. Greater relative separation (greater distance between the subject and background in relation to how close you are to your subject) will result in smoother out-of-focus areas for a given focal length lens and aperture.
When shooting close-in to your subject, you will often find that as long as the important areas of your subject (stamen on a flower, or leading edges of the petals, etc.) are sharply in focus, it is OK to limit your depth of field and let areas of your subject that are farther away go just a little soft in order to softly blur the background. You should use your depth of field preview or live view, or zoom into the image on your camera's LCD to evaluate whether or not the background is sufficiently blurred to remove distractions and provide pleasing bokeh. Since it is often difficult to judge the bokeh of an image until you see it "full size" on your computer's display, I will often "bracket" my apertures, shooting the same scene with a range of aperture values (and adjusting the shutter speed accordingly) in order to provide a range of choices from which to select my final images.
The assignment for the week of 28 March - 3 April 2011 is "Bokeh." You should attempt to control your depth of field and separation between your primary subject and any foreground or background elements in order to produce aesthetically pleasing out-of-focus areas in your images. Please upload your images to the "Bokeh Revisited" album in the Weekly Assignments category of the gallery no-later-than midnight Mountain time (GMT -07:00) on Sunday, 3 April 2011.
(Because we are out at the ranch this weekend, with a glacially slow internet connection over an ancient phone line, I might not have the opportunity to post example images until our return home.)
I will look forward to seeing your images.
