From: andpph@ritvax.isc.rit.edu
Newsgroups: rec.photo
Subject: Re: multiple exposures
Date: 11 Jan 93 00:46:24 GMT
Reply-To: andpph@ritvax.isc.rit.edu
Organization: Rochester Institute of Technology

In article <C0ntLs.81E@comp.vuw.ac.nz>, jenny@gphs.vuw.ac.nz (Jenny Rollo)
>writes: I have been reading the May 1992 issue of "The National Geographic" 
>magazine, and have been marvelling at the photography for the article 
>entitles "The Great Eclipse".  On the first pages of this article, there is a 
>multiple exposure photo from start to finish of the total solar eclipse which
>took place on July 11th 1991.  ....
>Firstly in this photo there are obviously 28 different exposures on the one 
>frame.  Each frame is well exposed and my quest(ion is):
>1) what sort of exposure time might be used for this type of photograph?  
>It is taken at nightfall and I can't see (I know nothing about this!) how you 
>can get a long enough exposure without showing the Earth's movement and 
>without overexposing the observatory, also shown in the picture.  
>2) My other query is that a person is standing on top of the observatory, arms
>outsretched.  How can he have registered clearly on the film, surely he would 
>have had to stand in this pose for some time.

I am at a disadvantage because I do not have the picture in front of me... but
I do remember seeing it and it was truly a spectacular shot. Was it taken by
the same person who took the year-long photo of the sun at the same time of day
every so often with the sun describing a figure 8 in the sky?

So, in my opinion, the first part of the picture was made by making a
sequential series of shots onto the same piece of film loaded into a camera
firmly attached to an immovable support at regular intervals. Since the sun is
so very bright each exposure can be made through a very dense grey filter and
thus the foreground is not exposed at all but the sun appears properly exposed
at different stages of the eclipse. The only part of the eclipse for which no
neutral density filter would have been used is totality. This would have also
made a significant exposure of the observatory, however. It could have been
masked or shaded by the photographer to prevent this from happening. The
eclipse itself took place with the sun quite high over the horizon and not at
twilight. 

This leads me to believe that the following process was then used to
expose the other part of the picture, that of the observatory and man with
outstretched arms It could have been made either before or after the eclipse,
when the sky was already very dark. The exposure, if I recall correctly,
indicates that some sort of auxiliary lighting was used to illuminate the scene
and it was either flash(es) or local tungsten lights. 

The basic idea is that during the exposures of the sun the observatory appeared
too dark for the film to record it properly and during the exposure of the
observatory the sun was gone from the sky and the light available at the
observatory was sufficient to produce a good image with an exposure time of a
couple of seconds or so. Or with flash, which hopefully would have no effect in
lighting up the stars! :-)

Please not that this is all conjecture! Maybe someone who has the actual photo
in front of them can explain it better. In fact, I thought that the process was
explained in the back of the issue or maybe even within the text. They say two
things go with age.... thank goodness it is my memory!

Andy

        *  *  * * *  *
         \/\/\/\/\/\/   Andrew Davidhazy, RIT, High Speed Photography Lab.
          |        |    IN%"andpph@ritvax.isc.rit.edu"    fax 716-475-5804 
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