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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old July 11th, 2009, 08:21 AM   #1
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Is this diffraction?

You would think after almost 400 posts I would have asked for advice on my footage by now...well here goes. These are some screen grabs from a recent gig. I'm not sure if this is the best way to get feedback? I will try to post footage tomorrow when I have more time. The client pointed out to me that the models faces were a little distorted at times. Did a quick search, and seems like the problem may be diffraction?? I think the footage is good, but not broadcast worthy.

(from left to right)
1st image: .mov, 2300kbps
2nd image: .mov, 6000kbps
3rd image: .mov, 2300kbps
4th image: .mov 600kbps

2nd and 4th images show the next frame after the others, in which the distortion is more apparent. I don't know if this should be happening?

My settings, to my knowledge, were as follows:
Panavision preset (or was it vividrgb, looks like panny right?)
f1.8
1/48
24f
+6db
standard def


JS
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Is this diffraction?-screenshot.jpg  
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Old July 11th, 2009, 08:43 AM   #2
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no - diffraction is caused by small apertures. Using f1.8 you won't get diffraction but you may get a shallow DoF which can also lead to soft focus, particularly when subject is darker than bg
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Old July 11th, 2009, 01:34 PM   #3
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yeah there wasn't much light there, but I thought it would be enough for the gig. So is the problem here a soft focus? I didn't bother focusing manually because all the models were not walking to the same location on the stage, and AF has worked great in the past. Sometimes I did have to do a quick manual focus though because I know it's difficult for the AF to function in lower lighting conditions.
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Old July 12th, 2009, 03:17 AM   #4
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was there a dirty sky light filter or something screwed on the end of the lens?

Ian
Festival Video and Audio Previews - Festival Previews Ltd
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Old July 13th, 2009, 08:51 AM   #5
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shooting at f1.8 in auto focus with a moving subject in front of a bright background you are almost certainly going to have problems with soft focus.
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Old July 13th, 2009, 11:34 AM   #6
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Also shooting at 24f in auto focus in any condition is not a good idea , adding the low lighting condition will make the auto focus a bigger problem.
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