Archived posting to the Leica Users Group, 2003/08/08

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Subject: Re: [Leica] More on lag measurement
From: Martin Howard <mvhoward@mac.com>
Date: Fri, 8 Aug 2003 19:11:41 -0700

LRZeitlin@aol.com wrote:

> You don't even have to use film. The flash will illuminate the 
> position of
> the marble and you or your friend will be able to mark how far it has 
> dropped on
> the meter stick. [...]
>
> This simple test is about as accurate as they come.
>

Again, accuracy is not the issue -- validity is.  Like so much 
experimental psychology, for the purpose that you are trying to use 
these results, this experiment is simple, elegant, accurate, and almost 
totally irrelevant.

Pretty much the only case where a photographer is facing this kind of 
task is trying to catch the very first motion of a swimmer diving off 
the platform, or a sprinter's first push out of the blocks.  But even 
in *those* cases (reaction to stimuli without preceeding rhythmic or 
timing context) you're typically interested in action that takes place 
slightly later: the swimmer's hands breaking the water's surface, or 
the runner with one foot in the blocks, the other on the ground, and 
leg extended.  So, again, it's about timing: stimuli -- beat -- shutter 
release.

For the very vast majority of photography, adding a 200 ms human 
reaction time to whatever the camera's shutter lag may be is completely 
meaningless in any sense other than the mathematical one.

M.

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Replies: Reply from Ted Grant <tedgrant@shaw.ca> (Re: [Leica] More on lag measurement)