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budlegallee
Joined: 06 Sep 2008
Posts: 1
Location: Alto, MI
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 Posted: Sat Sep 06, 2008 5:10 pm Post subject: GRAFLEX XL SPACERS |
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When using the XL Spacers do you need to increase exposure? If so does any one know the additional exposure needed for the different size spacers? 
_________________
Digital What? |
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Dan Fromm
Joined: 14 May 2001
Posts: 2144
Location: New Jersey
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| Posted: Sat Sep 06, 2008 5:26 pm Post subject: |
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It isn't that simple.
The relationship between effective aperture and aperture as set is: effective aperture = (aperture set) * (1 + (magnification/(pupillary magnification)).
For some of the lenses made for the XL pupillary magnification is around 1. I'm not sure about the 58 Grandagon.
Magnification = 1 + (extension from infinity position/focal length)
The spacer increases extension from the infinity position by its thickness, but since the lens is on a focusing helical it can be focused closer with the helical. That's why there's not a fixed relationship between the spacer's thickness and effective aperture given focal length.
Sorry it isn't simpler and easier,
Dan |
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