READ THIS ONE- Studio Photography

Hello there,
            This discussion's been a good test for the
tolerant spirit that prevails in this list. Reading
the archives I can see that there have been some
controversies in the past, but they have been more
about "shape" than "substance". In this case, is
different, is about a technical approach of one of the
members that tho it works perfectly for him, it
plainly defies, the laws of Physics.

Just having to fire 4 times the flash needed for f/45
to go from f/45 to f/128 is equivalent to having an
exposure of f/5.6 with 1 secs (non flash photo) and
just give 4 secs when using f/16, when we all know 8
secs is the correct exposure time (not including
reciprocity corrections).

For up to 3 stops separation (i.e: f/45, 64, 90 , 128)
the exposure difference between the member's method
and the mandated by laws of physics is just 1 stop,
which may or may not be noticeable, depending the
latitud of our photo emulsion.

To the couple of members that raised the original
question: the laws of physics state that the numbers
of "pops" of flash needed is equal to 2 multiplied by
itself as many times as stops separate the initial and
final apertures. For initial f/45 and final f/128,
there are 3 stops of separation, therefore the number
of "pops" would be 2x2x2 = 8
The above is valid when the flash is fired from the
same position and angle. If the multiple firings of
the flash is from different positions, the above
approach is not valid. Now that I think, this could be
the case for the member using the 1 pop per stop
approach, in which case the flash position "KEY" is
the one that we should be taking into account
(mainly).

All the above does not include any reciprocity
correction that may be needed.

Regards,

A_list_observer

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Received on Wed Nov 22 09:41:11 2000