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Alternative Imaging Methods
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Old September 6th, 2005, 10:06 PM   #1
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filter & vortex

Hi !

To avoid vortex-effect with an old version of the mini35 ,an added filter on the lens is a good thing to reduce the luminosity ?

And to use a very dark filter will result at same effect of vortex that to reduce a little too much the relay lens ?

excuse my english again !

Daniel Limoges
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Old September 9th, 2005, 08:49 AM   #2
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Hello Daniel,

The quick answer is yes, using filters in front of the lens is a good way to control the light.
However the vortex becomes more visible when the exposure of the center of your frame is lower. So you will get better results if the illumination near the center can be maintained a little high. This assumes that you are keeping your film lens at T4 our wider.
Yes the filtration in front of the lens has a similar effect as the iris on the relay lens.

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Old September 19th, 2005, 06:36 PM   #3
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Merci Guy !
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Old September 20th, 2005, 07:38 AM   #4
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Hi,
This is new term for me, "vortex" ?
I believe I am not a lone.
Could somebody write few words about it, Charles ?
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Old September 20th, 2005, 09:15 AM   #5
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Hello Pekka,

Yes theses terms do get confusing don’t they; Daniel used the expression “vortex-effect” to describe the swirl motion of the grains in the center of rotation of the ground glass. This was a problem with the early design of the Mini35 where the center of rotation was in the middle of the image. With the current Mini35, that is series 400, the ground glass has an eccentric motion thus correcting this problem.

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Old September 21st, 2005, 11:54 AM   #6
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Thanks Guy,
I was guessing something like that, but to know is so much better!
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