Bokeh

Bokeh (虚化 / 焦外成像) is a photographic term that describes the aesthetic quality of the out-of-focus areas in an image produced by a camera lens.

It is not the blur itself, but rather the way the lens renders that blur—specifically, the shape and visual characteristics of the blurred light sources, highlights, and transitions in the background and foreground.

The word "Bokeh" comes from the Japanese word boke (暈け or ボケ), which means "blur" or "haze."

Key Characteristics of Good Bokeh

Photographers generally describe "good" or "pleasing" bokeh as being:

1. Smooth and Creamy: The transition from sharp to blurred areas is gradual and soft, making the background look like a smooth, painterly wash of color.
2. Circular Highlights: Out-of-focus points of light (such as streetlights, reflections, or distant bulbs) are rendered as soft, perfectly round or pleasant geometric shapes.
3. No Hard Edges: The bright, circular highlights do not have distracting, harsh, or brightly outlined edges.

Poor Bokeh (or "Busy" Bokeh) is often described as having:

• Harsher, Distracting Edges: Highlights have hard, bright rings (sometimes called "onion rings" or "cat's eye" shapes) that draw attention away from the subject.
• Double Lines: Background elements that are rendered with distracting double outlines.

What Determines the Quality and Look of Bokeh?

The quality of bokeh is almost entirely determined by the lens and the settings used.

1. Lens Aperture

• Maximum Aperture: Lenses with a wider maximum aperture (a smaller f-number, e.g., f/1.2, f/1.4, f/2.8) can create a much shallower Depth of Field, which leads to more background blur and thus more pronounced bokeh.
• Number of Aperture Blades: This is the most critical factor for the shape of the bokeh highlights.
  • Lenses with more aperture blades (e.g., 9, 11, or 15) and a circular diaphragm design will render the out-of-focus highlights as perfect circles, even when the lens is stopped down slightly (e.g., from f/1.4 to f/2.0).
  • Lenses with fewer blades (e.g., 5 or 7) will render the highlights as a distinct polygon shape (a pentagon or heptagon) when stopped down.

2. Focal Length

• Longer Focal Lengths: Telephoto lenses (e.g., 85mm, 135mm, 200mm) naturally compress the perspective and create a shallower depth of field, exaggerating the background blur and the size of the bokeh highlights.

3. Subject-to-Background Distance

• The greater the distance between the subject and the background, the more the background will be thrown out of focus, making the bokeh effect more pronounced and softer.

Common Usage

Bokeh is most commonly utilized in photography genres where the subject needs to be isolated from the background, such as:

• Portraits: To draw the viewer's eye directly to the person's face.
• Macro Photography: To isolate the tiny subject (like a flower or insect) from a messy background.
• Food Photography: To highlight a specific dish or element on the plate.

In essence, Bokeh is the signature or aesthetic fingerprint of a lens's ability to render the unsharp areas of an image beautifully.