Bokeh v Depth of Field

JSD · Dec 13, 2009

I posted this in another thread but now that I see there are several other threads on the subject I thought it might be worth its own thread. Dwig gave a better technical description of what determines bokeh, but I hope mine helps to clear up the difference between the two terms:

I think that there is a miss use of the term "bokeh". Bokeh is a word derived from the Japanese word boke, pronounced so that it sort of rhymes with okay and means out of focus (or it can also mean senile). What it has come to mean in photography is the nature or charcteristics of the out of focus area in a picture. The term depth of field refers to the zone of focus, the area in a picture that is in sharp focus, not the characteristics of the out of focus areas. Bokeh is determined mostly by the shape of the leaves of the diaphragm, and cannot be controlled by the photographer (unless, as Dwig said, he buys a differant lens). Depth of field is controlled by the photographer when choosing an aperture, and by the focal length of the lens. Wide angle lenses have inherently more depth of field and telephotos, less. For a given lens a smaller aperture, for example f16 will have deep depth of field, and a wide aperture, such as f2.8, much less. Lenses used for landscape are usually short focal length, stopped down to a small aperture, say f16 or f22, hence the great depth of field between the flowers in the foreground and the snowcapped peaks in the distance. A shot of a bird, with limited depth of field where only the bird is sharp with the background blurry was likely taken with a telephoto lens at a wide aperture, say f2.8 or f4. Now the nature or characteristics of the blurry part of the bird shot, for example a point of light, although out of focus, might be nicely rounded or it may have angular edges, that is bokeh.

DScience · Dec 13, 2009

It's not complicated. Bokeh is out of focus light, it's a word. From that there are tons of variations of bokeh, different types and uses for bokeh, and different qualities. Also, the photographer CAN control in many situations how the final product (bokeh) looks. There are many factors that affect it, and the cameras aperture blades are just ONE factor.

KmH · Dec 14, 2009

DScience said:
It's not complicated. Bokeh is out of focus light, it's a word. From that there are tons of variations of bokeh, different types and uses for bokeh, and different qualities. Also, the photographer CAN control in many situations how the final product (bokeh) looks. There are many factors that affect it, and the cameras aperture blades are just ONE factor.

Here's a great explanation from a similar thread and link.

Dwig said:
From the horse's mouth:
The Online Photographer: What Is Bokeh?

Mike Johnston, the author of the linked essay, coined the term "bokeh" and created its definition. He borrowed a Japanese word that is properly spelled in Latin characters as "boke" and added a trailing "h" so that English speakers would pronounce it more correctly.

Discussions of bokeh generally center more on the quality of the blur rather than the quantity. Quantity is merely a factor of depth-of-field (DOF). The quality of what blur is present is a factor of a number of optical and mechanical aspects of the lens and is out of the photographer's control other than his choice of lens.

The shape of the aperture is commonly mentioned as a major factor because its easy to see and describe, but its actually a minor factor in the quality of the bokeh except when the shaped is odd (e.g. catadioptic mirror lenses and their donut shaped aperture). Also, the iris blade shape only affects the aperture shape at apertures other than the maximum. The nature of the balance of optical corrections for spherical aberration and other corrections have the largest effect.