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Old Nov 19, 2006, 1:01 AM   #1
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My Rebel 350 D + Kenko extension tubes + Sigma 70-300, 4-5.6 APO DG Macro (or 18-55 kit Lens) gets very soft images - I think!

What could be the reason?


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Old Nov 19, 2006, 1:02 AM   #2
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Pic. nr. 2
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Old Nov 22, 2006, 9:10 AM   #3
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Hi vidiac!

I'm not a real close up expert, but what I DO know is that with macro photography one often needs to be aware of the thin DOF (small depth of field) one has. A quick calcuation of your settings in these 2 photos (1st one f5.6 at 190mm, 2nd one f20 at 300mm) on this website http://www.dofmaster.com/dofjs.htmlreveals if you were near the CLOSEST focusing distance of your sigma lens (e.g. around 1 metre) then your depth of field was only around HALF a centimetre (that's only a few millimetres!)

As in BOTH shots the subject is not straight to the lens (that is, the grasshopper is facing the camera, more or less!) so part of the body is closer, part is further, then only a PART of the length of it's body will be in focus! I can see part of the insect in focus, and part NOT in focus. That's just because of the incredibly small depth of field with a lens at either 190mm or 300mm and photographing things at CLOSE distance!

anyway, that's what I think / conclude! I might be wrong, but I think the problem in these photos is not lack of SHARPNESS, it is lack of DEPTH of FIELD.

I hope this might be helpful

Paul

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Old Nov 22, 2006, 11:05 AM   #4
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Thank you!

I forgot to mention that these pictures are a bit adjusted regarding sharpness, so the originals are more soft.
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