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Sounds from IS

What is the sound that high-end (L) Canon lenses make? These are the
new lenses with image stabilization. I have not heard it myself but it
was described to me as very slight whir - constant in intensity.

Thanks,
Ron
 
T

Tim Auton

Jan 1, 1970
0
What is the sound that high-end (L) Canon lenses make? These are the
new lenses with image stabilization. I have not heard it myself but it
was described to me as very slight whir - constant in intensity.

I've got no L lenses, but I do have a Canon EF-S 17-85mm IS (Image
Stabilization) lens for my 20D. I'd never noticed any constant noise
before (the focus and aperture motors make noise, but only
intermittently). Putting my head right next to it and trying with IS on
and off, the IS does indeed make a constant buzzing/whirring sound noise
while it's active.


Tim
 
S

Sjouke Burry

Jan 1, 1970
0
Tim said:
I've got no L lenses, but I do have a Canon EF-S 17-85mm IS (Image
Stabilization) lens for my 20D. I'd never noticed any constant noise
before (the focus and aperture motors make noise, but only
intermittently). Putting my head right next to it and trying with IS on
and off, the IS does indeed make a constant buzzing/whirring sound noise
while it's active.


Tim
Thats because there is a small giro motor,wih
a mirror attatched,compensating your movements.
 
T

Tim Auton

Jan 1, 1970
0
Sjouke Burry said:
Thats because there is a small giro motor,wih
a mirror attatched,compensating your movements.

In the diagram of one I saw it's not a mirror, but a lens assembly. But
essentially, yes - there is a mechanical device moving about inside the
lens to provide the IS and it's that which is making the noise. The
other system in use (generally on compact cameras) involves taking a
rapid sequence of images with the CCD and shifting and recombining them
in software. This is cheaper to do than physically moving optics about,
but increases the readout noise by orders of magnitude as you're reading
the CCD numerous times per 'frame'.


Tim
 
Tim said:
In the diagram of one I saw it's not a mirror, but a lens assembly. But
essentially, yes - there is a mechanical device moving about inside the
lens to provide the IS and it's that which is making the noise. The
other system in use (generally on compact cameras) involves taking a
rapid sequence of images with the CCD and shifting and recombining them
in software. This is cheaper to do than physically moving optics about,
but increases the readout noise by orders of magnitude as you're reading
the CCD numerous times per 'frame'.


Tim

I originally thought the sound was related to a gyro but there is
widespread agreement in my camera newsgroup that motion detection for
optical image stabilization in lenses is done using solid state devices
not the kind of mechanical device you're talking about. There is
speculation that the sound is made by motor control circuitry used to
move the optics. What kind of motor controller makes a constant whir
sound?

Thanks,
Ron
 
T

Tim Auton

Jan 1, 1970
0
I originally thought the sound was related to a gyro but there is
widespread agreement in my camera newsgroup that motion detection for
optical image stabilization in lenses is done using solid state devices
not the kind of mechanical device you're talking about. There is
speculation that the sound is made by motor control circuitry used to
move the optics. What kind of motor controller makes a constant whir
sound?

It seems much more likely that the sound is coming from the actuators
which move the lenses; that is the mechanical device I was referring to
rather than a classic gyroscope in the form of a significant rotating
mass. That is the bit that moves significantly, so that seems to be the
most likely source of the noise. The stabilising action comes not from
gyroscopic action directly, but from a feedback loop fed from gyroscopic
sensors. The sensors I expect will be MEMS devices, which aren't really
solid-state as they do have moving parts, albeit incredibly tiny moving
parts which make no noise.


Tim
 
Tim said:
It seems much more likely that the sound is coming from the actuators
which move the lenses; that is the mechanical device I was referring to
rather than a classic gyroscope in the form of a significant rotating
mass.

I see.
That is the bit that moves significantly, so that seems to be the
most likely source of the noise. The stabilising action comes not from
gyroscopic action directly, but from a feedback loop fed from gyroscopic
sensors. The sensors I expect will be MEMS devices, which aren't really
solid-state as they do have moving parts, albeit incredibly tiny moving
parts which make no noise.


Tim

It is my understanding that the noise is non-intermittent and continues
even when the camera is placed on a tripod. Presumably this is some
kind of polling behavior. Why is it necessary and why does it make a
noise?

Thanks for the time,
Ron
 
T

Tim Auton

Jan 1, 1970
0
I see.


It is my understanding that the noise is non-intermittent and continues
even when the camera is placed on a tripod. Presumably this is some
kind of polling behavior. Why is it necessary and why does it make a
noise?

I think you'd have to ask a Canon engineer or someone who's had one to
pieces and run a bunch of tests - unfortunately I'm neither.
Speculating, I don't find it surprising that the actuator would always
be moving (and thus making noise) while the system is active. Any sensor
will produce some level of noise in its signal (in the electrical,
rather than accoustic sense), as will the electronics betwen the sensor
and actuator. This noise can be translated to small movements of the
actuators back and forth around the desired position. Damping that
noise, electronically or mechanically, would degrade the response of the
system to rapid changes. It's not unusual for control systems to
oscillate a little around their desired operating point, particularly if
they are optimised more for rapid response than minimum overshoot and
oscillation.


Tim
 
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