Bokeh. Thoughts about bokeh.
This article is very filled with subjective opinions. Be patient with patience and understanding.
Bokeh is the “character” of an image outside the focus area, its intensity, and the effect on the overall picture. Roughly speaking, this is how a blurry image is out of focus. The term “blurry” is not entirely technical, but it is as suitable as possible to describe what is happening with the image not in the focus area. The image is “blurred” as if the artist picked up and mixed paint.
When focusing, the camera sharpens only those objects on which the lens focuses. All other objects in the frame are not sharp. With this, objects can be very blurred, or blurred just a little bit. Usually, the picture clearly shows the area in which objects are sharp. This zone can be measured in width (depth).
The width of this zone corresponds to the depth of field of the lens – the depth of the sharply imaged space. English analogue DOF. Bokeh is directly related to the area of unsharpness, which is the other side of the depth of field. Therefore, by influencing the depth of field, you can objectively influence the bokeh.
The following parameters are responsible for the intensity (strength) of the blur (bokeh):
Lens focal length. The greater the focal length of the lens – the easier it is to achieve a blur background, increase the degree of blur.
Aperture lens. The larger the relative aperture (the smaller the F number), the easier it is to achieve a strong blurring of the image in the non-zone of sharpness and to increase the circles of blurring outside the zone of the DOF.
View of the opening of the diaphragm. Usually, the diaphragm at closure cannot remain as round as when fully open. This is due to the limited number of diaphragm blades. When the diaphragms are closed, instead of disks (circles, roundels), polygonal shapes appear in the blurring area.
Focusing distance. The closer the focus position to the MDF (minimum focusing distance), the stronger the blur will be. Therefore, even on a “dark” lens, you can get a good blur by taking close-up objects when the lens is focused as close as possible. Conduct an experiment, take your whale lens (or any other), turn off the automatic focus, install the MDF and try to remove some little thing, such as a pot, a cup of tea. Then look at the area of unsharpness, it will be very blurred.
The optical scheme of the lens, which, in fact, forms an unusual pattern for each lens separately. Personally, I think a good optical scheme with a nice bokeh, a Sonnar type circuit. But now, just a sea of other good lenses with incomprehensible multi-line schemes and pleasant bokeh. The optical scheme of some lenses, such as the Nikon AF DC-Nikkor 105mm 1: 2 D Defocus Image Control, has a special ring for bokeh control.
Indirectly affects the size of the matrix. Simply, with the same lens for the same composition (frame composition) with a different matrix size there will be a different focusing distance, therefore, the blur intensity is higher. More detail in the section on Crop Factor.
Background and foreground. It is very important that there is an understanding that the blur pattern depends on what will be blurred. Bright single light sources usually turn into luminous discs, and a uniform background into soft plastic porridge.
You can, of course, still use soft filters, gradient, point filters for blur.
Objectively, we can only speak about disks in the unsharp zone, their size, type, and shape. I call these discs “rounds”. The disks have a special feature – the transition from the light inside to the darker outside. Bokeh, in which the discs have a small border width, is commonly called “fish scale”.
The shape of the light spot (disk) is highly dependent on the shape of the diaphragm. With a maximum aperture, almost all fixed lenses give a smooth “hole” in the aperture. When you close the diaphragm, its petals form all sorts of patterns. The most frequent are nuts, circular saws, rectangles, squares. The form can be made by yourself. Below is a snapshot of the usual 7-coal nuts.
What types of bokeh are there?
Usually, in western literature there are two types of bokeh: Hollywood Style (Hollywood Style Bokeh) and cream bokeh (Creamcheese Bokeh). I almost never saw separation into these two types anywhere in the CIS, but, I adhere to such a simple gradation.
Hollywood bokeh with discs (circles) in the blur area
Bokeh with discs (circles) in the blur area
Hollywood bokeh (Hollywood Style Bokeh) – bokeh, in which luminous circles (disks) are pronounced in the blurring area.