Boke this (via English bokeh < from Japanese ボケ - blur) - the nature of the picture given by the lens in the blur zone.
What is bokeh
Boke This is the Japanese name for the out-of-focus area, essentially the background image behind the subject. Each lens has its own out-of-focus pattern. With zoom lenses, the blurring is quite harsh - both geometric and color are noticeable. proportions objects following the subject of the photo. For lenses with a fixed focal length, "fixes", background blur can reach unimaginable values.
Typically, the subject is clearly separated from the background. A big difference is noticeable when comparing photographs taken with a “reportage” universal lens, and more “artistic” fixed focal length lenses. In terms of magnitude, I would compare it like this: the out-of-focus pattern at an f / 2.8 zoom will be approximately identical to a fix at f / 4-5.6, at the same focal lengths.
Bokeh and optical design of the lens
Of course, a lot still depends on the optical design itself. This, by the way, is the reason for the predilections of various categories of photographers for various lenses - due to the peculiarities of the optical scheme, different optical schemes give a different artistic effect, - for some lens has a signature swirling background, the other has an oil paint effect. Lenses known in the post-Soviet space are twisting the background almost free of charge, without registration and SMS Helios 44.
The Japanese, in general, consider any manifestation of background elements in the blur area at low f / aberration, and value even colors (that is, the elements behind the object are blurred stupidly to a state of color, without any hint of proportions). Of course, despite all this, a high-quality portrait can be shot with a zoom lens. It all depends on the experience of the photographer.
Aperture blades and their effect on bokeh
The number of aperture blades in lenses varies. Typically, low-cost lenses are equipped with few petals. On bоAt higher f / values, fewer petals will produce jagged circles (“nuts”) of light sources in hips... Sometimes you can find a star-shaped aperture at the lens - with a small number of blades, this solution adds some artistry to the drawing of the out-of-focus area. The photo below shows diaphragm lens Industar-61 L \ Z MS.
Industar-61 L / Z 50mm f / 2.8 and the Ricoh Rikenon 28mm f / 2.8 are brilliant representatives of the star-aperture lens caste with a small number of blades in the mechanism. The shape of the aperture formed by the aperture blades can be ignored if we are going to shoot, and not look at the blurred light sources in the background.
How to see bokeh
Anything in the out-of-focus area will be considered bokeh. You can see it through the lens of the camera, without having taken a picture yet - for this, it is enough to focus on the focus. The best background blur usually occurs at the closest focusing distance.
What does bokeh depend on?
Bokeh depends on the focusing distance and the set aperture value. A larger aperture setting produces a harder blur, while a smaller aperture produces a more blurred background image. Also, the nature of the background blur depends on the optical design of the lens. Zoom lenses tend to have less artistic blur.
Using programmatic methods, for example, you can change the nature of the blur zone. The easiest way, in a photoshop program, for example, is to use the tool blur toolbar of the program. In smartphones, as a rule, due to the quality of the optics and the size of the sensor, the bokeh is always harsh, similar to the wide-angle lenses of full-frame cameras. In order to mitigate this disadvantage, software methods of image processing are used. for example, in the "portrait" mode of a smartphone - the software prudently blurs the background and smoothes the skin of the subject's face.
How to reshape bokeh highlights
The shape of the flare in the blur area depends on the aperture formed by the lens aperture blades. It can be square or diamond-shaped, as is the case with a lens. Helios 44M1, so it may look like a star (example with bokeh above). The glare in the background can be of any shape. Previously, kits were sold on eBay with different shapes of the center hole, allowing installation on the front lens of the objective. Using such a kit, you can change the shape of the glare to a snowflake, key, heart, and so on.