here is a video workshop by Gordon Laing, Editor of Camera Labs....
http://www.dslrtips.com/workshops/How_t ... ield.shtml
And to take a photo like the one you have linked to:
1- put the lens to manual focus
2- use the closest focus point you possibly can (opposite of infinity)
3- use the largest aperture you can. (in your case f/3.5 or 5.6)
4- snap the picture
And Three tips for getting shallow depth of field
1- large aperture (f/2.8 and larger works best, larger meaning f/2.0, 1.8, 1.4, 1.2 and so on)
2- shoot telephoto. 70mm will provide you with a much better bokeh than 18mm.
3- distance from subject. the closer you are to your subject the more shallow the DOF. The further your subject is from your background the more it is knocked out.
Example:
Notice in this image I took earlier today...
1- I shot this image at f/2.2
2- I shot this image at 50mm not telephoto but on a cropped canon body its 80mm which is a sweet spot for portraiture.
3- I am very close to my subject, my subject is very far away from the background.
the perfect combination for shallow DOF (depth of field)
...hope that helps
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Canon 40D + 70-200mm f/2.8L IS + 50mm f/1.8
Manfrotto 055CX3 + 496RC2
www.thomaslowe.com