Bokeh? What’s that all about then?
Well, I’ll tell you what that’s all about.
Essentially bokeh is the effect we all love in photographs, especially in portraiture. The subject of the image is in sharp focus, but the background is a creamy, dreamy blur.
See that blurry background bit? That’s bokeh, that is.
Now, it gets a little more complex than that, but bokeh is a fancy word that describes a blurry background. To go a little deeper, the word itself is Japanese (translates as “blur” or “hazy” - you get the drift) and the Wikipedia definition is “the way the lens renders out-of-focus points of light”.
So, now that we know what it is, how do we get it? That’s where it can get a little tricky as well as, sadly, expensive. The faster your lens the better, ideally f2.8 or faster – but faster lenses tend to mean higher prices. Alas.
However, achieving bokeh with a slower lens is not impossible – you just need to try and ensure a greater distance between the subject and the background, effectively ensuring the background falls out of the depth of field in the image.
Depth of field is affected by aperture and distance from subject. For example, f2.8 with a subject 5 feet away with create a narrower depth of field at the same aperture if the subject is 50 feet away. There are online “depth of field” calculators that will give you an idea of how this works in practice. This link is one good example
So, with that logic in mind, achieving bokeh at f4 or slower is not impossible as long as distances are managed. One other factor that will help is shooting at a longer focal length, for example 100mm instead of 35mm
Being closer to the subject and having a greater distance from subject to background while using a long focal length helps in the bokeh process. So, aim for these four factors
Fastest aperture you have available
Move closer to subject
Have greater distance between subject and background
Longer focal length
This is not my image, as a disclaimer - it’s a stock shot but shows how bokeh affects points of light out-with the depth of field in an image. This tends to be a classic idea of bokeh.
This is one of my images, shot at a relatively slow f5.6. This is an example if how distance between subject and background can help create that blur.
Shot at f3.5, the aim here was to have the main flower in focus and those in the background blurred, for the bokeh effect but retaining the overall context of a yellow field of flowers.