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# 6 01-12-2002 , 01:40 PM
kbrown's Avatar
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Join Date: Sep 2002
Location: London, UK
Posts: 3,198
Hmm..Ok, I got your point.

Let's take this issue a little further because this might not be clear for everyone. With the Focus Distance you control what objects are sharp at which distance. With the fstop you just control how deep is the focused area. This way you can get blurred foreground, in focus middle area and blurred background.

Focal Length and Focus Region Scale (this is a synthetic setting not found in real cameras) has also a big effect on the DOF effect. By increasing focal length you also increase the blur effect. With the focus region scale you can adjust the sharp area artificially. Personaly I leave this at it's default setting of 1.0.

Here's a real world example. In my Canon XL1s I have fstops from 1.6 to 16 (and close). In the footage I have a large iris (fstop = 1.6) and rather big focal length (zoomed in). Only thing I'm controlling here is the focus ring (focus distance). First the fence in foreground is sharp while everything else is blurred. In the middle of the video both the fence and the trees in the background are blurred but some area of the rain in between is sharp (except for the motion blur). In the end both the rain and the fence is blurred but the trees at background are sharp.

I hope this makes any sense...

The file is about 950 kB


Kari
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