[MF3D.FORUM:334] or a ouija board

[Tom Deering <tmd@xxxxxxxxxxx>]

On 3/28/00, Stuart Johnson wrote:
>Finally, if Tom's formula is correct ( Base = 1 in FL of Lens )
>then if I have a 100mm Base with my Hassy's and use 80mm
>lenses, then the CLOSEST I can have my foreground is...  26 feet.
>This can't be right....

I can hear some of you chuckling.  Calling it *my* formula is like 
calling bacon "kosher".

You want a rule?  Here's a *real* rule:

# Because light travels very fast, almost instantaneously, it is possible
# to estimate the distance between an observer and a thunderstorm from the
# time difference between the lightning flash and the thunderclap. The
# "rule of thumb" is that every five seconds time difference corresponds
# to a mile distance. Is this correct? In imperial units sound travels at
# approx. 0.2 mile/second (actually 0.214 mile/s) thus in five seconds
# one mile is covered by sound and the "rule of thumb" is about right.

*This* rule is everything the "1/30 rule" isn't.  It's just what it 
seems to be.  There are no special cases that invalidate it.  It's 
not wildly off under common circumstances.  Even a child can get 
within 7% the mathematically correct solution in their head.

By comparison, the "1/30 rule" is a ouija board.  Witness the many 
misapplications of it in this thread alone.

Can we talk about something else?  Astrology, maybe?

Cheers,

Tom
--
Tom Deering  --  voodoo@xxxxxxxxxxx  --  http://www.deering.org