Re: [OM] Ambient and Flash Ratio Tutorial

Subject: Re: [OM] Ambient and Flash Ratio Tutorial
From: Winsor Crosby <wincros@xxxxxxxxxxxxx>
Date: Thu, 14 Feb 2002 14:53:12 -0800
 > Excellent tutorial, but I do have one quibble:
 While focal plane synch limits the *fastest* shutter speed
 to 1/60, you can certainly use a slower shutter speed if you
 want to.  At the extreme, that's how you combine a
 flash-exposed subject underneath a six-hour star trail
 exposure.  So if you really want to stick with your slow
 film, you can do it with a slower shutter speed.

What you are suggesting is true, but does reverse the sequence
slightly.  You are defining the aperture first and then the
shutter speed last.  Just like using a leaf-shutter camera--with
a speed limitation of 1/60 instead of 1/500.  Your example is a
special case where you have defined your other four variables
first.  The fact that you have selected an illustration of very
long time exposures means that the shutter speed limitation
actually does not exist.

The primary purpose of the tutorial was to work around the
normal limitation of 1/60.  Most of our cameras force flash sync
at 1/60 when using auto modes.


Absolutely superb explanation, Ken. I wish I had read something like it years ago.

I think the 1/60 second limitation is a good idea. Otherwise you might require the addition of a tripod to the mix.
Winsor Crosby
Long Beach, California


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