"Bokeh" In photography, bokeh (originally /ˈboʊkɛ/,[1] /ˈboʊkeɪ/ BOH-kay — also sometimes pronounced as /ˈboʊkə/ BOH-kə,[2] Japanese: [boke]) is the aesthetic quality of the blur produced in the out-of-focus parts of an image produced by a lens.[3][4][5] Bokeh has been defined as "the way the lens renders out-of-focus points of light".[6] Differences in lens aberrations and aperture shape cause some lens designs to blur the image in a way that is pleasing to the eye, while others produce blurring that is unpleasant or distracting—"good" and "bad" bokeh, respectively.[7] Bokeh occurs for parts of the scene that lie outside the depth of field. Photographers sometimes deliberately use a shallow focus technique to create images with prominent out-of-focus regions. (https://en.wikipedia.org/wiki/Bokeh)

All the sample images illustrate bokeh. The term "bokeh", a noun, alone often isn't sufficient without further explanation. Saying "bokeh" without a descriptive adjective is like saying "camera" without saying what type of camera it is, or like stating "color" or "light" without any further explanation of their qualities.

Whether it's "good" or "bad" bokeh is in the eye of the beholder, too. Bokeh can be described as harsh, strong, heavy, light, creamy, crazy, dreamy and many other ways using any number of adjectives.
Further, a lens might be able to produce both "good" and "bad" bokeh. It's subjective (eye of the beholder) and what's "good" for one subject might be "bad" for another... and vice versa. The characteristics of bokeh are determined by aperture used, focal length, design of the aperture (i.e. number of blades, curved blades), distance to the subject and distances to other objects within any given scene, and even by the subject itself and the scene as a whole. In fact, ISO, post-processing and other factors can effect bokeh, too.

Part of the original posters "problems" aren't defined... she doesn't say in her post what it is about the bokeh she likes or dislikes in each image. Part of the difference between them are that in the first three images the background is much closer behind the subject than in the fourth... also in the fourth the bacground gradually falls away to increased blur, while in the other three it appears the backgound is mostly on a single plane. And there are a number of large, strong, specular highlights in the first three images... while they are more distant and smaller in the fourth. And, the first three images were shot as ISO 1000, 1000 and 1600.... while the fourth was shot at ISO 320.

I can't tell if those images were shot as JPEGs or RAW or if there was significant adjustment made to them. But if 8-bit JPEGs, especially if there was some increase in exposure in post-processing, granularity and banding can be increased, while at higher ISO resolution is somewhat reduced. Working with RAW instead, which are shot 14-bit by the camera but interpolated and handled as 16-bit files by post-processing software, especally if doing any cropping or significant adjustments to color, exposure, contrast, curves, and levels. While it's fine and often preferable or even necessary to save an image as an 8-bit JPEG, it's best when working on it that it be in 16-bit mode, in part to make for the smoothest and nicest looking blur effects. The method and amount of sharpening done to an image also can make significant difference.

In fact, there are post-processing "tricks" that can be done, to improve bokeh effects. For example, the lens that I used to make the shot below tends to render a rather coarse background blur... especially when the background is busy and there are strong specular highlights. So I applied some selective blur and selectively reduced the contrast of the background, as well as using the burn tool to reduce the brightness of some of the background highlights....


Here's a color image with the same lens but also shot at ISO 3200 where I did similar, selectively adding blur to the background, although the background was quite distant and specular highlights weren't a problem. In this case I also applied sharpening very selectively, too, only to the subject itself (after resizing and cropping the image, which is also important)...


Local conditions at the time you took the shot can make a big difference, too. Such as the foggy background here...


The shaded background (a fence and wood pile) in the image below also helped a lot...


The lens used for the above flower image was a 500mm "mirror"... which are renowned for the "donuts" they create around out of focus specular highlights and a lot of people find objectionable. Here are more shots with the same lens, where you can see some of those occurring because the background isn't completely in shade...


IMO, bokeh also relates to foreground blur... how a lens renders out-of-focus objects between you and the subject... not just how it renders blur of OOF objects beyond and behind the subject...


Time of day and ambient light conditions effect bokeh, too.... Planning around when a background will be shaded, rather than sunlit can help... or wait until your subject moves to a more favorable location. I like to shoot on overcast days or in shade, when possible... then use the lens aperture and distances to control the strength of background (and foreground) blur, as seems appropriate to the subject. Complete and utter blurring into nothingness isn't always the goal...

Thank you amfoto1 for taking the time to post the in depth info and examples. It is a great help and I will save this information for future use. Your photography is fabulous to say the least!


I also appreciate all the other UHH'ers input and explanations.

Many mentioned that I should do a comparison but I cannot compare the old and the new as I did trade the lens in. I guess my main concern was the lines going through the highlights. I have never had that problem with any other lens and to me it was distracting. So I will watch my background when composing and of course keep an eye on my Fstop, distance, etc. Also as mentioned the new Sigma is a "sharper" lens than the old which could definitely be part of the difference. I am also able to edit out areas that are an issue to me as amfoto1 mentioned.

Thank you everyone for taking the time to respond. It was very educational.
Have a great week!
Sharon/Clicker

True indeed, but your comment is a non-sequitur! Shooting at f/9 doesn't mean the entire image is necessarily in focus, and in those examples there are significant areas with out of focus blur where bokeh is a point of interest! Who cares if it has "maximum background blur"? That it has some background blur, where the character of that blur is important to the perceived quality of the image, is the point of significance.

And when grading a lens it is very important to know that bokeh does or does not degrade as the lens is stopped down. For example, in years past when the Nikkor 85mm f/1.4 was "The Cream Machine" a lot of people repeatedly recommended the less expensive 85mm f/1.8 as a nearly equal replacement, which it was not! The f/1.4 lens had rounded diaphragm blades, and bokeh remained pleasant (and actually got better for the first stop or so) as the lens was stopped down from wide open. The f/1.8 lens was only nice when shot within a half stop of wide open, and went down hill fast from there. There was no comparison at f/4, as an example.