Wide Aperture - Need a little help with focus

[cgipson1]

A blurry background is not bokeh.

Bokeh is not adjustable, but a blurry background is.

Bokeh is the subjective visual quality of blurred image elements.
Lens construction, the number and shape of the lens aperture blades, the quality of the glass lens elements, all determine the bokeh quality a lens will produce.

The only way to change the bokeh is to use a different make/model of lens.

trying to keep it simple...

 

[TCampbell]

A blurry background is not bokeh.

Bokeh is not adjustable, but a blurry background is.

Bokeh is the subjective visual quality of blurred image elements.
Lens construction, the number and shape of the lens aperture blades, the quality of the glass lens elements, all determine the bokeh quality a lens will produce.

The only way to change the bokeh is to use a different make/model of lens.

You can control the "intensity" of it, but you can't control the "character" of it without changing to a different lens.

You certainly can have some bokeh which is "better" than others -- good bokeh vs. bad bokeh. So we can still call it bokeh even when the quality is poor.

The Canon EF 50mm f/1.8 lens only has 5 aperture blades and defocused points blur to a pentagonal shape rather than a circle. This causes a non-uniform blur especially noticeable with contrasty highly textured backgrounds. As the points in the image are defocused, the defocused points overlap in a non-uniform way and the result is a segmented jittery effect. It's often referred to as "nervous bokeh". Lenses with more circular rounded aperture openings tend to produce an effect which is smoother and well-blended for a more pleasing effect.

To help understand the "quality", here's a site which compares Canon's three different 50mm lenses (the f/1.2L, the f/1.4, and the f/1.8 "nifty fifty"). He posted a magnified section from each photo so you can see the shape of the blur as well as the effect it has on a background with a lot of texture (in this photo it looks like it may be tall grasses or perhaps some branches.) The f/1.2L creates the most rounded shape and also the smoothest bokeh. The f/1.4 does a respectable job. The f/1.8 does a mediocre job (and that's possibly being kind.) Note that the "intensity" of the bokeh is the same since they were all taken with 50mm lenses at f/2.8. But the "quality" of the bokeh is NOT the same.

 

[weepete]

True, but there seems to be a lot of people mixing up bokeh with blur. I'm all for keeping it simple but oversimplification can lead to confusion.

Bokeh as far as I'm aware is the quality of the background blur by definition.

We are all getting off topic anyway.