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12-04-2006, 01:15 AM   #1
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Do I have a front focus problem?

My DS focuses behind this point!




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12-04-2006, 04:18 AM   #2
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I'm not sure what's your point and I dont see any indication of focus malfunction in attached images.
12-04-2006, 04:26 AM   #3
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Have you tested with your D-SLR? My DS when focused at the same point has much more in focus at rear compared to the front.
12-04-2006, 05:50 AM   #4
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What lens?

12-04-2006, 08:49 AM   #5
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Looks good to me.
12-04-2006, 09:47 AM   #6
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QuoteOriginally posted by peted Quote
My DS when focused at the same point has much more in focus at rear compared to the front.
It should. Roughly 1/3 of the dof is in front of the point on which you focus, 2/3 behind, if I recall correctly. I'd say your lens/camera is behaving exactly as it should.

Julie
12-04-2006, 12:00 PM   #7
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I can't see any problem here, at all.

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12-04-2006, 12:02 PM   #8
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Foxglove - question

You stated that the focus should be 1/3 out front and 2/3 behind the focus. Could you explain why this should be so. Would like to learn. Thanks.

12-04-2006, 12:05 PM   #9
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Looks spot on to me. However, it looks like you did not shoot the focus target at a 45 degree angle. Looks more like 60 or so.
12-04-2006, 12:06 PM   #10
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QuoteOriginally posted by clarenceclose Quote
You stated that the focus should be 1/3 out front and 2/3 behind the focus. Could you explain why this should be so. Would like to learn. Thanks.
Ack! I might've known someone would ask... and I don't have a good answer. It's something basic to do with the optics of lenses, but darned if I can remember the details. Time to go dig out the old photography books...

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12-04-2006, 12:09 PM   #11
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I'll see if there is anything in my resources too. Just thought it had something to do with the DSLR lenses. Thanks.
12-04-2006, 03:13 PM   #12
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I would consider this as a perfect focus
12-05-2006, 02:29 AM   #13
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The 1/3 2/3 thing is not what it "should" be Clarence, it is was it is.

When focussed on a point, of the area that is within acceptable focus, 1/3 will be closer to the lens than the focussed point, and 2/3 will be further away. That's just how it is. All lenses.
12-05-2006, 03:36 AM   #14
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With some basic knowledge of lenses I quickly sketched this drawing witch should explain why depth of field is deeper behind the plane of perfect focus and thinner in front.



Oh, you have to click on the image for a larger version.
12-05-2006, 09:36 AM   #15
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Thanks for the graphic and the explainations. Then because of the 1/3-2/3 lense DOF, I would assume that has a lot to do with the recommendation, expecially on a landscape shot, that one would focus on something that is 1/3 into the photo, not on infinity, so the DOF of the lense, based upon the aperature setting, would make the photo more effectively focused and give a correct relationship to the eye. i.e. things in the distance are not really in sharp focus nor are things at our feet when we look at a view. ??
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