If I've got this right, you have to consider the distance that your subject is from the background. You might try your test with a subject that is moveable and see if that's makes a difference. The further away from the background, the more "blurred" the background will be. Also, the focal length of the lens might be a factor in your results. I don't know that with a 16 mm focal length, you'll get the bokeh that you are looking for.
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Lori Putman flickr
~No one can drive us crazy unless we give them the keys
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