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Old Nov 8, 2006, 10:49 AM   #1
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i have been seing a lot of imagess taken using different macro lens's. Why is the short focal length macros have exceptionally narrow dof while long tele(150,180) have comparatively broader dof.

Especially 60mm and 90mm lens's have such a beautiful dof that except the point of focus the rest of the image as a very beautiful smooth bokeh.

I have been viewing a lot of images from Pbase and even from my friends.

I just wanted to know if the focal lenght has something to do with DOF. I even experienced this using a simple 50mm where the more nearer one is to the subject the better the bokeh.,

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Old Nov 8, 2006, 11:28 AM   #2
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DOF is controlled by several factors:

focal length of lens (all else being equal a longer focal length produces shallower DOF)

Size of sensor / film

distance to subject (all else being equal, distance to subject produces shallower DOF - this is where focus distance of macro lenses really comes into play - being able to get within a couple of inches of your subject makes a huge difference)

aperture value used (all else being equal, the wider the aperture the shallower the DOF)

In addition, the blur of the background i also controlled by the distance between the subject and the background (e.g. if your dof is 1 foot then a background 2 feet behind subject will be very much in focus but a background 100 yards away will not - DOF is the same in both cases - 1 foot - but background blur is different).

Here is an article that explains DOF:


You can also use this calculator to figure out DOF for a given set of criteria:


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Old Nov 8, 2006, 1:10 PM   #3
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For a macro there is no difference of DOF at the same magnification (i.e. longer working distance, but also longer focal lenght) - see link:
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Old Nov 8, 2006, 4:49 PM   #4
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Thanks John and NHL.

Very Userful

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