There's been lots of talk about using IS with tripod.
I found this interesting article on usenet news. Haven't
seen this here yet, so here comes..
-------- Forwarded message --------
Newsgroups: rec.photo.equipment.35mm
Date: Sun, 25 Feb 2001 22:03:58 GMT
From: "Don Cohen" <[EMAIL PROTECTED]>
Subject: Re: canon 28-135 IS
Hi Ron,
Chuck Westfall of Canon supplied this detailed answer on IS and tripods
at
Rob Galbraith's D30 forum. I doubt he would mind being quoted here. It
is
a very comprehensive answer, so a bit length, but worth the space:
Begin Quote:
>>The instruction sheets with my IS lenses say to turn the IS function OFF
when using a tripod. I have heard other photographers argue the
opposite.
Would you discuss the pros/cons of this?<<
The answer depends on which type of IS lens you're talking about. With
the
IS super-telephotos (300/2.8L IS, 400/2.8L IS, 500/4L IS and 600/4L IS),
it's OK to leave IS turned on when the lens is mounted on a tripod. For
all
other current IS lenses (28-135/3.5-5.6 IS, 75-300/4-5.6 IS,
100-400/4.5-5.6L IS, and 300/4L IS), it is much better to shut off the
IS
function when the lens is mounted on a tripod.
Here's the explanation for the 28-135 IS, 75-300 IS, 100-400L IS, and
300/4L
IS lenses:
>>The instruction manual warns that the IS stays on after pressing the
shutter button half way, and that use of IS on a tripod may damage the
lens.<<
Here's what the instruction book says (page E-8): "Do not set the image
stabilizer switch to 'I' when using the camera on a tripod. Doing so may
cause the image stabilizer to act erratically. Turn the image stabilizer
off
'0' before using the camera on a tripod."
There is no language here or anywhere else in the instructions
concerning
damage to the 28-135 IS caused by using the camera on a tripod. All
they're
saying is that using IS while the camera is on a tripod "may cause the
image
stabilizer to act erratically."
>>Why does tripod use cause a problem?<<
Short explanation: The IS mechanism operates by correcting shake. When
there
is no shake, or when the level of shake is below the threshold of the
system's detection capability, use of the IS feature may actually *add*
unwanted blur to the photograph, therefore you should shut it off in
this
situation.
Longer explanation: Remember that the IS lens group is normally locked
into
place. When the IS function is active, the IS lens group is unlocked so
it
can be moved by the electromagnetic coil surrounding the elements. When
there's not enough motion for the IS system to detect, the result can
sometimes be a sort of electronic "feedback loop," somewhat analogous to
the
ringing noise of an audio feedback loop we're all familiar with. As a
result, the IS lens group might move while the lens is on a tripod,
unless
the IS function is switched off and the IS lens group is locked into
place.
>>Is IS best kept off, then turned on for each shot as needed, then turned
off again, much as one would use the exposure compensation dial?<<
For most hand-held work, leave the switch on; for tripod work, shut it
off,
as noted in the instruction book.
The recommendations above do *not* apply for the 300/2.8L IS, 400/2.8L
IS,
500/4L IS, and 600/4L IS. Here is some information for them:
>>[with 300/2.8L IS, 400/2.8L IS, 500/4L IS and 600/4L IS] Does IS operate
when the lens is on a tripod or not??<<
I can positively confirm that it does, and quite well as a matter of
proven
fact.
>>The Owner's Manual (page 12) says it does not.<<
We know. But our testing indicates otherwise.
>>Canon Inc.'s EF Lens Tech Report (Vol. 13) implies that it disengages but
then says it stabilizes when using a tripod.<<
I see no such implication. My copy of this report says: "With previous
IS
lenses, it was necessary to turn off the Image Stabilizer when using a
tripod because it might operate incorrectly. But the Image Stabilizer
installed on these IS lenses has an additional function that prevents
improper operation when using a tripod. It also corrects camera
vibration
caused by slow shutter photography when using a tripod: a common problem
with Super Telephoto lenses. About one second after the shutter is
pressed
halfway, the unit automatically determines that a tripod is being used
from
the output of a vibration gyro." These statements are 100% accurate
based on
my testing. There are no other references to the use of IS on a tripod
anywhere in this report, as far as I can tell.
>>My own guess is this. When the tripod/head is rigid and there is little or
no vibration, IS does disengage. When you loosen the head -- as for
following birds in flight -- the gyros sense some vibration and the IS
begins to operate again.<<
This is not quite right. Based on my own personal testing and
observation,
as well as a personal consultation with one of Canon
Inc.'s chief executives in the Lens Division, these lenses effectively
have
2 IS modes *within Mode 1.* The decision on which mode will be used is
made
by the equipment, not the photographer, based on an evaluation of the
degree
of detected movement, as follows:
A. When the lens is mounted on a steady tripod and the shutter button is
pressed halfway, the IS begins to operate immediately and the image in
the
viewfinder goes through a very slow vertical shift for about 1 second.
After
that, if the shutter button continues to be pressed halfway, the IS
mechanism automatically goes into a special mode which is designed to
detect
and correct for mirror slap and shutter movement
at slow shutter speeds. Based on my personal testing, it does this job
spectacularly well. Close examination of results from shooting tests
definitively proves that there is no advantage to be gained by shutting
off
IS, or even by locking the mirror prior to exposure.
B. When the lens is mounted on a monopod or hand-held *and* the gyro
sensors
detect movement exceeding a certain rate, the IS mechanism switches into
its
conventional correction mode which is designed to compensate for
relatively
gross and/or erratic lens movement.
So, what you're seeing when you loosen the ball head and start moving
the
lens is essentially an automatic switchover from "tripod IS" to
"conventional IS."
Best Regards,
Chuck Westfall
Assistant Director/Technical Information Dept.
Camera Division/Canon U.S.A., Inc.
End Quote
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