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Old 11-10-2011, 01:08 AM
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PCH (Paul)
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PCH is offline
Join Date: Feb 2007
Location: Perth WA
Posts: 2,183
Hi Mariusz and Andrew,

thanks so much for replying. I feel like a total wal' asking this question. I'm experimenting with some simple features of the camera, starting with depth of field.

If we go to page 68 of the manual, in my copy this section is headed "Av - Changing Depth of Field"

The image example I'm interested in is the picture on the left, - the 'blurred background'. I do actually understand what I'm looking at and how it's supposed to be achieved. I just can't, for the life of me, get my 400D to produce this image.

I find that when I set the top wheel to 'Av', if I set the standard lens to 18mm (wide angle/distant) everything is pretty much in sharp focus, with a very wide DoF, which is what I'd expect.

But when I zoom in to my subject by turning the lens to the 55mm f/l extreme, I would expect to find a narrow DoF would be available. Instead, I'm finding that once zoomed in (set to the 55mm setting), the largest the aperture will go is f5.6 - versus f3.5 at the 18mm lens setting. And this 5.6 f-stop setting prevents me from obtaining an image with a narrow depth of field.

The DoF I can produce of the chess board setup as on Pg68 of the manual has nothing like the narrow DoF that the pic in the book has.

Am I doing something wrong guys? Would you mind checking your 400Ds please? All suggestions much appreciated
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