Joe U. wrote:
> Here's one thing Bryan Geyer has to say about tripods:
>
> Why is a tripod essential?
>
> Because blur due to lens movement is inevitable at any shutter
> speed slower than 1/1000 sec., and because it promotes greater
> care in composition. Handholding is strictly for dead photographers:
> A human pulse beat will cause 200 microns (about 0.008 inch)
> displacement for 1/10th second. Assuming a shutter speed of
> 1/250th sec., this movement alone will cause a 22% loss of
> resolution with a system that is otherwise capable of reproducing
> 100 lines-per-mm (lpm). And at a shutter speed of 1/125th sec.,
> this performance would degrade to only 53 lpm-a 47% waste of
> what you purchased. (Refer John B. Williams: Image Clarity,
> page 191)
>
>
>
> If you don't recognize the name, he runs Really Right Stuff.
Geyer, I assume you mean. John Williams is a computer programmer in
California. Or was, last I knew.
Incidentally, what his reference says (_Image Clarity_ p. 191) is that a 200
micron displacement CAN be caused by a pulse, not that it "will cause" it.
And Williams's tables are plainly stated to show THEORETICAL system
resolution losses--a far cry from Mr. Geyer's "blur due to lens movement is
INEVITABLE." Theory doesn't always translate to practice.
I might also mention that various "star point" tests have proved that "safe
shutter speed" parameters vary not only between between individuals but
between cameras. Some cameras are actually _less_ capable of being held
steadily at 1/1000th than at 1/250th, ostensibly because of sympathetic
vibrations in the mechanism.
Also, elsewhere in _Image Clarity_, John Williams points out that ground
vibrations can defeat even the best tripod. Ever stood on a busy traffic
bridge as traffic passes, so you can feel the bridge vibrate up and down?
Well, the same thing on a smaller scale happens most of the time in most
places in most cities. Surveyors have devices to measure ground vibration.
As ever, the best thing to do is make a test for yourself. Get an ND filter
or two and your tripod, head outside, and shoot the same subject with a
tripod, and handheld at every shutter speed down to a second. Compare the
results.
You might be surprised at what you discover. <s>
--Mike
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