It actually increases as the square of the distance, i.e. twice the distance
requires 4 times the light, 4 times the distance requires 16 times the
light.
Jerry in Houston
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
Sent: Thursday, April 26, 2001 9:11 AM
To: [EMAIL PROTECTED]
Subject: Re: Teleconvertor suggestion
What you've discovered is the inverse square law. When you do bellows or
extension tube work, your exposure has to increase when you extend your
bellows or use of tubes. This is not in a linear fashion but increases
proportionately with the distance. If (and this is the important if) your
flash is attached to the front standard of the bellows or the filter ring of
your lens, whenever you extend your bellows the amount of light the flash
puts on the subject will increase also. But again it will not increase in a
linear amount depending on the extension but in proportion to the square of
the distance.
Both of these cancel out, as you have found out through experimentation.
Congratulations for empirically finding this out.
W
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