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Old Nov 28, 2006, 10:35 AM   #11
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use this chart at a 45 degree angle for calibration test

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Old Nov 28, 2006, 1:20 PM   #12
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Also it's probably worth mentioning that the DOF is also a function of the distance from the frame to the subject.

For instance if yourfocus pointis 30ft from the sensor, at 50mm and f1.7 your DOF is aprox 9 and a half feet. If your focus point is 2 feet from the sensor with the same 50mm f1.7 your DOF isabout half an inch. At it's closest focus of 1.5ft, the DOF is under one quarter inch.

By f5.6 though you've tripled those DOF's (keeping in mind that at 1.5 ft you're still only looking at a three-quarter inch DOF) so DOF should be less of a problem.

There are known issues with some KM DSLR's focusneeding re-calibrationalso. KM was recalibrating them but I haven't heard of anyone sending one in for this in quite some time. I'm not sure what Sony's policy is for this. If you have focus issues with more than 1 good quality lens, I'd look toward having the camera serviced (or replaced if you just got it).
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Old Nov 28, 2006, 2:58 PM   #13
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Sorry you are right I mis-spoke or typed what ever the word may be This is the first day I've been out of bed in 2 days Nasty nasty bronchial infection
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Old Nov 29, 2006, 9:13 PM   #14
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bernabeu wrote:
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use this chart at a 45 degree angle for calibration test
how do you use this calibration test. Are there steps needed to come up with the rights results?

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Old Nov 29, 2006, 9:58 PM   #15
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Gobs wrote:
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bernabeu wrote:
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use this chart at a 45 degree angle for calibration test
how do you use this calibration test. Are there steps needed to come up with the rights results?

Thanks0
I believe you hold it at a 45 degree angle and focus on the center and take a shot. The middle of the chart should be in focus and the parts of the chart closer and farther away from center should be out of focus if you are shooting wide open or at wider apertures. You can then chose to have it calibrated or if you are bold and brave, you can try to calibrate it yourself. Someone can correct me if I'm wrong.
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Old Nov 30, 2006, 9:22 AM   #16
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Gobs wrote:
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bernabeu wrote:
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use this chart at a 45 degree angle for calibration test
how do you use this calibration test. Are there steps needed to come up with the rights results?

Thanks0

print chart on photo paper

set camera on sturdy tripod

set f stop to 1.7 (or your largest available aperture from a prime lens)

mount chart at 45 degree angle about 3-4' from camera (or point camera at 45 degrees to chart)

set auto focus selector to center spot

frame center focus 'square' on center line of chart and allow camera to lock focus on the center line

the resulting image should be sharpest at the center line and (hopefully) sharp for some distanc ahead and behind

if the image is sharper behind the center lineyou have a 'back focus' issue (somewhat common with the 7D)

IMO: do NOT attempt to adjust yourself - all the AF sensors must be calibrated in THREE planes

KM used to use the 50mm f1.7 and a computer to make the adjustment(s)

proper AF at f2.8 :


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Old Nov 30, 2006, 4:51 PM   #17
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Keep in mind that your DOF at 4 ft and f1.7 (50mm) is 3/16 of an inch. At f8 you're DOF is just over 3/4 inch which would be easier to judge focus lock. Or you could increase the distance but that solution has problems also. ( the camera may not focus exactly on the paper where you think it should, or the photo may be hard to properly read) Either way, it may be easier to diagnose gross focus problems using books on a table at varying distances from the camera.
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