Is there a difference between Bokeh and DOF?

[Parker0485]

Probably a dumb question but I've seen people referring to the blur effect on a photo as 'Bokeh' and to me it looks like same thing as DOF.

Is there a difference? Or is Bokeh just a word to refer to the DOF effect?

 

[Gary Coyle]

Depth of field is what is actually in focus at any given aperture, Bokeh is simply what the out of focus background looks like

 

[Decca]

Bokeh is the out of focus background you get when focusing on something in the foreground. DOF is depth of field and is the area that is in focus

edit: durn.

 

[Parker0485]

So you use DOF to achieve a bokeh?

 

[Decca]

Correct. I am assuming you have a cup of tea or coffee on your desk, if not then yell "somone make me a brew". Set up your shot so that the cup is is in focus, set your camera to whatever canon call aperture priority and take three photos at a low middle and high F number and you will be able to see the effect. When shooting this way, setting your iso higher will increase your shutter speed. You may now safely ignore the auto setting on your camera.

 

[Yv]

yes, basically, the narrower the depth of field [area in focus], the more area of 'bokeh' or out of focus blur there will be. Some people get positively dreamy when a good lens produces really lovely bokeh

 

[AndyB1976]

In simple terms yes. A small DoF will create a larger area out of focus.

However bokeh itself generally means the quality of the out of focus area. This can be influenced by the optics and also the aperture size, the number of blades and their shape.

Quality bokeh is subjectively smooth and rounded, whereas the poorer quality can be more angular.

http://www.the-digital-picture.com/Reviews/Canon-EF-50mm-f-1.8-II-Lens-Review.aspx (second image here)

 

[Parker0485]

Thanks guys

 

[EdBray]

Bokeh is a word which is derived from the Japanese word for 'blur' and is used to describe how a lens handles out of focus areas. This is not just down to the focal length and aperture used (which will give the same depth of field as any indentical focal length used with the same aperture) but is very much more attributable to the design, number and style of aperture blades and the type of glass used in the lens. It is also very much down to personal interpretation.

Depth of Field is the area of perceived sharpness in front and behind of the actual focus point. This can be increased or decreased by changing the aperture of the lens, Decreasing the f no (increasing the actual size of the aperture) will decrease the depth of field and Increasing the f no (decreasing the actual size of the aperture) will increase the depth of field.

The lower the depth of field the more out of focus areas there will be in the image and thus the more the 'bokeh' of the lens will show. Usually the 'bokeh' is at it's best for a lens at it's maximum aperture, as in this case the aperture blades are usually not used and the aperture is just a complete circle.

 

[Parker0485]

Thanks, that's cleared it all up

 

[HoppyUK]

So you use DOF to achieve a bokeh?

Yes. It is one of the factors, probably the easiest to control with aperture, but a lot depends on your definition of bokeh. There's quite a lot of debate about that, but in popular terms it usually means lots of blur, with big out of focus highlights.

If that's what you mean/want, then the three things to do are move the subject as far from the background as possible and really fill the frame (to create maximum distance differential), then move back with a longer lens to narrow the field of view and 'enlarge' the background. Then use the lowest f/number.

Two pictures to illustrate that, both at f/4, which shows it's not all about low f/numbers. Depth of field is identical in these two pictures, it's the field of view that changes.

70mm f/4

200mm f/4