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Old July 27th, 2005, 01:07 PM   #1
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Fix one problem and another starts - barrel distortion

I think those that have this DOF thing perfected are complete geniuses and I applaud them wholeheartedly - now onto my nightmare...again.

Well, it seems when I get one thing fixed - mainly the spread of light evenly and vignetting - and another one props up . I am getting major barrel distortion from the condenser - after looking at the footage a second time, I am noticing that straight line, poles etc are bananaing and curving - a product of the condenser. I have tried |) (| to fix it, but to no avail. Again, I applaud those that seem to get this thing right the first time and those that have been at it for a long time and are tinkering, but I just can't seem to get it right (broken record).
Someone was using PCX lenses, I am wondering if they are getting the same problem?
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Old July 27th, 2005, 01:39 PM   #2
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I think people are doing the optical path like this :-

Subject >> SLR lens (| >> GG >> |) >> Dioptre or close-up lens >> camcorder.

If I read your post correctly, your condensers are facing the wrong way. The flats should be closest the groundglass. Both condensers as I understand it, should be identical. There are people here accomplished in this department so do not take too much notice of this commentry.
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Old July 27th, 2005, 03:03 PM   #3
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Thanks Bob, I tried that too, but just get more distortion. I am going to have to find a couple of tried and true condensers to really see if this is going to work. I am also back to blurring around the edges of the frame problem as well. I was doing some tests to see what a wire looks like in the middle, left and right, well needless to say the middle looked great, but the left and right were blurry.
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Old July 27th, 2005, 11:23 PM   #4
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are you using some kind of tiffen or hoya macro??? that will cause distortion around the edges if you have a poopy macro...
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Old July 28th, 2005, 02:16 AM   #5
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Quote:
Originally Posted by Mandy Leo
well needless to say the middle looked great, but the left and right were blurry.
How big is the condenser you are using ? Maybe it too small. I used just one with diameter about 8cm and worked well.
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Old July 28th, 2005, 07:22 AM   #6
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Yes it is too small I think, about 45mm - I am going to try and find another one that is about 7-8cm like you have and see what difference it makes. The trouble is now, do I get a DCX with two rounded sides or just the one?

Dave, what was the focusing screen type again? Was it Nikon D? I wonder what the 'T' and the other letters represent?

Last edited by Leo Mandy; July 28th, 2005 at 09:33 AM.
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