Bokeh Is Japanese for Blur
Bokeh is the often-mispronounced term for those wonderful round, out-of-focus highlights that we love floating throughout the backgrounds of photographs. So just what is photographic bokeh and how does it differ from a blur of the same name made in Photoshop? The answer this time in the «Digital Photographer’s Notebook.»
There are three factors that make pleasing bokeh: pinpoint highlights, a lens with a longer focal length than normal for the camera, and a large aperture. Surprisingly, the most beautiful bokeh is not always with the widest f-stop. Oh, by the way, Japanese speakers say «bo-KEH,» not «BO-kay.»
CAMERA SENSOR FORMATS
Let’s clarify how to distinguish wide angle from telephoto for full-frame and cropped sensor cameras. It’s really simple and holds true for any camera format. «Normal» focal lengths are the diagonal measurement of the sensor in millimeters. Full-frame cameras have sensors 24x36mm. The diagonal is 43.27mm—round it up to 50mm for normal. Most cropped sensor cameras are 22.7×15.1 mm. That diagonal is 27.3mm. The nearest standard is 28mm. Here’s how simple this is: once you know what normal is, any lens whose focal length is less than that is wide angle; any lens with greater-than-normal focal length is a telephoto.
DEPTH OF FIELD, FOCUS, AND WIDE-OPEN APERTURES
Wide-angle lenses provide greater depth of field than tele-photos. More depth of field means more of the subject is sharp in front of and behind the actual point of focus. That’s important when the goal is creating a background with beautiful bokeh.
Surprisingly, the widest opening of the aperture of a lens is not the best choice for creating a sharp photograph with beautiful bokeh. Take a look at this photograph of Robot B-9 GUNTER* from Lost in Space photographed with a full-frame Canon 5D Mark II and a Sigma 85mm lens at f/1.4. The background highlights are large, very soft, and slightly elliptical in shape. The subject suffers. Look at the inset. The front of the robot is tack sharp, while the antennas are out of focus. Another issue with working at any lens’s maximum aperture is increased color fringing around edges of high contrast known as chromatic aberration.
Closing down two stops from f/1.4 to f/2.8 makes a huge difference. Robot B-9 is now acceptably in focus, and while the bokeh is a bit smaller, now it’s round. Roundness is determined by the number of blades making up the aperture: the more blades, the rounder the bokeh. This lens has nine of them.
Compare the bokeh of two more apertures, f/5.6 and f/11. As the aperture gets smaller, the depth of field increases and the background comes more into focus. With more of the background in focus, the bokeh circles get smaller. At f/11, they’re almost gone.
Here’s what we know: As the background goes out of focus, the highlights get larger and dimmer. The same pinpoint of light at f/11 spreads over a much greater area at f/1.4. It’s the same amount of light hitting the background, so as it covers more of it by being out of focus, it loses brightness. To illustrate this get a flashlight. Move it close to a wall. It covers a small area. Move it away from the wall, and the area covered by the light gets bigger and dimmer—same thing with focus and blur.
BLUR IN PHOTOSHOP
Photoshop CS6 has some new photographic blur tools: Field Blur, Iris Blur, and Tilt-Shift. Let’s see how these digital effects work compared to their lens-created counterparts. Download the sample file from the NAPP member website to follow along.
step one: Open the file Robot B-9.tif in Photoshop CS6. Duplicate the background layer by pressing Command-J (PC: Ctrl-J). Double-click the new layer’s name and rename it «Bokeh.» step two: In the Paths panel, Command-click (PC: Ctrl-click) the path named f/11 to make it into a selection. Press Command-Shift-I (PC: Ctrl-Shift-I) to invert the selection. This protects Robot B-9 from the effects of the next step.
step three: Choose Filter>Blur>lris Blur. The Blur Gallery displays a preview of your blur. Press-and-hold the Shift key, and click-and-drag the outer oval in the image to make it smaller and circular so the blur covers the entire back¬ground. In the filter’s Options Bar, set Selection Bleed to 0%, Focus to 75%, then turn on the High Quality check¬box. Next, in the Blur Tools panel, under Iris Blur, move the Blur slider to 59 px. Now here’s the magic: In the Blur Effects panel, under Bokeh, move the Light Bokeh slider to 33%. You’ll notice some completely white blooms in the background. That’s okay. Move the white Light Range control to 245. The other one controls how much of the midtones receive the bokeh effect. Click OK in the Options Bar. This filter requires some computational horsepower, so it may take a minute. When it finishes, press Command-D
(PC: Ctrl-D) to deselect. The result? Not too bad! And B-9 is sharp front to back!
DIGITAL OR PHOTOGRAPHIC? NOW IT’S YOUR CHOICE!
True to expectations, the background is out of focus with dimmer highlights in a bakshish shape. Here are photographic versions at f/1.4 and f/2.8. Compare them to the digital version.
This is where lines are drawn as to which one is better. I’m not going to go there! The results are different. Which to use is a creative choice. So, grab your camera and play with photo¬graphic bokeh, knowing you have options when you get your images back to Photoshop.
Next time, the «Notebook» continues its exploration of the Blur Gallery. Until then, keep shooting!