Archived posting to the Leica Users Group, 1999/10/10

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Subject: Re: [Leica] Lag time
From: Doug Herr <>
Date: Sun, 10 Oct 1999 03:06:42 -0400

Lag time is a big deal to me.

In many cases it's difficult to predict when a bird's head will be
positioned to catch the light just right, or how long it will be there. 
Those danged critters can rocket from here to nowhere in the wink of an
eye.  I want a minimum time lag between the decision to make the exposure
and the actual event, but the time between pressing the shutter release and
the start of the exposure is only a piece of the story.

Ignoring for now my own reaction time, other factors that influence lag
time are the time to frame the image, the time to focus, the time to set
the correct exposure and the much-discussed (lately) shutter release lag. 
Comparing lab measurements of which-camera-has-the-shortest-lag are
interesting factoids but I'm more interested in the total lag from brain to

Auto-exposure by itself is quicker than lining up needles or diodes *if* I
expect the automatic setting to be correct.

The best auto focus is (supposedly) quicker than manual focussing *if* the
system locks on the the right target.

AFAIK there are no automatic features that will frame the image the way I
want it.  As it turns out this lag time is usually the limiting factor;
manual focus and setting exposure manually can very easily be done while
framing the image, using peripheral vision for the needles/diodes and by
locking the focus sensor (A.K.A. eye) on the main subject as soon as it's
in the viewfinder.  Sure, in a lab test, an automatic feature by itself
will beat setting things manually, but in the field, all that stuff is
happening simultaneously.   The quickest shutter-press-to-exposure time
does me no good If I waste my time waiting to the system to lock on, or
disabling something that's been fooled by tricky light, or mentally cursing
an awkward camera function.

Doug Herr