Help please - Optical image stabilization with telephoto adapter?

Some cameras, like Canon G9 and Canon S5 IS, have provision
for attaching a telephoto adapter or a wide-angle adapter.

If the camera has optical image stabilization, as do those
two cameras, will that stabilization still be effective with
the added zoom adapter?

Bob Cunningham wrote:
Some cameras, like Canon G9 and Canon S5 IS, have provision
for attaching a telephoto adapter or a wide-angle adapter.

If the camera has optical image stabilization, as do those
two cameras, will that stabilization still be effective with
the added zoom adapter?

Yes.

David

On Thu, 15 May 2008 10:02:48 GMT, "David J Taylor"

said:

Bob Cunningham wrote:
Some cameras, like Canon G9 and Canon S5 IS, have provision
for attaching a telephoto adapter or a wide-angle adapter.

If the camera has optical image stabilization, as do those
two cameras, will that stabilization still be effective with
the added zoom adapter?

Yes.

Thank you.

David

On Thu, 15 May 2008 10:02:48 +0000, David J Taylor wrote:

Bob Cunningham wrote:
Some cameras, like Canon G9 and Canon S5 IS, have provision for
attaching a telephoto adapter or a wide-angle adapter.

If the camera has optical image stabilization, as do those two cameras,
will that stabilization still be effective with the added zoom adapter?

Yes.

What David meant was that a zoom adapter will have no effect on the
proper functioning of image stabilization. He should have added that
any shaking that gets past the stabilizer will be magnified by the
added zoom.

I use a tripod when I care about my pictures, but that's just me. :-)

Paul Allen

On Sat, 17 May 2008 15:06:22 -0500, Paul Allen
said:

On Thu, 15 May 2008 10:02:48 +0000, David J Taylor wrote:

Bob Cunningham wrote:
Some cameras, like Canon G9 and Canon S5 IS, have provision for
attaching a telephoto adapter or a wide-angle adapter.

If the camera has optical image stabilization, as do those two cameras,
will that stabilization still be effective with the added zoom adapter?

Yes.

What David meant was that a zoom adapter will have no effect on the
proper functioning of image stabilization. He should have added that
any shaking that gets past the stabilizer will be magnified by the
added zoom.

I use a tripod when I care about my pictures, but that's just me. :-)

But a lady I know took a handheld picture of the angel on
top of the Mormon Temple in San Diego from about a half mile
away using her SX100 with maximum (40X) zoom. The angel
fills the frame--vertically--and is a good, sharp image. I
suppose she could have gotten a better picture using a
tripod, but to my eye it's not obvious that any improvement
is needed.

Maybe to a more expert eye there would be room for
improvement.

Now that I've said all that, I'm going to ask the lady to
send me a copy of the picture so that I can look at it again
and maybe put it on my Web site for others to comment on.

Speaking of tripods, I once learned a lesson that it took me
a long time to understand. I took some pictures with my
Canon A1 on a tripod, and they all came out quite distorted.
The faces looked like they had been stretched sideways as
the picture was snapped.

A long time later it occurred to me that I must not have had
the tripod adjusting screws tightened so that the reaction
from the mass of the focal-plane shutter movement was
causing the tripod to twist slightly when the shutter slid.

I've seen people with flimsy-looking tripods that looked
like they might give the same effect to some extent even
with things tightened properly. Is this a known problem?

Paul Allen wrote:
On Thu, 15 May 2008 10:02:48 +0000, David J Taylor wrote:

Bob Cunningham wrote:
Some cameras, like Canon G9 and Canon S5 IS, have provision for
attaching a telephoto adapter or a wide-angle adapter.

If the camera has optical image stabilization, as do those two
cameras, will that stabilization still be effective with the added
zoom adapter?

Yes.

What David meant was that a zoom adapter will have no effect on the
proper functioning of image stabilization. He should have added that
any shaking that gets past the stabilizer will be magnified by the
added zoom.

I use a tripod when I care about my pictures, but that's just me. :-)

Paul Allen

I don't carry a tripod around in my pocket, or on a field trip or visit to
the races. I find that Image Stabilised lenses suit my needs admirably.

When I want a much longer exposure I just find some natural object against
which I can brace the camera.

David

"David J Taylor" writes:
Bob Cunningham wrote:
Some cameras, like Canon G9 and Canon S5 IS, have provision
for attaching a telephoto adapter or a wide-angle adapter.

If the camera has optical image stabilization, as do those
two cameras, will that stabilization still be effective with
the added zoom adapter?

Yes.

Are you certain of that? It's not what I'd expect, though I don't have
such a camera to test.

Here's my reasoning: Suppose the adapter is a 2X telephoto adapter.
Suppose your hand holding the camera shakes +- 1 degree in one axis.
Because of the angular magnification of the telephoto adapter, the main
lens of the camera, looking through the adapter, sees +- 2 degrees of
angular motion, not 1 degree. The camera's acceleration sensors
detect the camera shake and move an internal lens element (or prism) by
the appropriate amount to cancel 1 degree of shake - not 2 degrees. To
properly cancel the larger apparent shake, the stabilization system
needs to double the gain of the system, in terms of compensation per
degree of shake motion.

The anti-shake system will automatically adjust its gain as required as
the main lens changes focal length via zooming, but it doesn't know that
the tele or wideangle converter is there.

Now, if the camera has a menu item to tell the camera that the tele or
wideangle adapter is currently mounted, ignore what I said above - the
camera does have the required information to set the antishake system
properly.

Also, if the magnifiying device is rigidly mounted and only the camera
shakes, then the stabilization would still work correctly. This might
be the case if you are handholding the camera at the eyepiece of a
telescope or microscope, shooting through the eyepiece. But not when
the camera and other optics are both shaking.

Dave

Dave Martindale wrote:
"David J Taylor"
writes:
Bob Cunningham wrote:
Some cameras, like Canon G9 and Canon S5 IS, have provision
for attaching a telephoto adapter or a wide-angle adapter.

If the camera has optical image stabilization, as do those
two cameras, will that stabilization still be effective with
the added zoom adapter?

Yes.

Are you certain of that? It's not what I'd expect, though I don't
have
such a camera to test.

Here's my reasoning: Suppose the adapter is a 2X telephoto adapter.
Suppose your hand holding the camera shakes +- 1 degree in one axis.
Because of the angular magnification of the telephoto adapter, the
main
lens of the camera, looking through the adapter, sees +- 2 degrees of
angular motion, not 1 degree. The camera's acceleration sensors
detect the camera shake and move an internal lens element (or prism)
by
the appropriate amount to cancel 1 degree of shake - not 2 degrees.
To
properly cancel the larger apparent shake, the stabilization system
needs to double the gain of the system, in terms of compensation per
degree of shake motion.

The anti-shake system will automatically adjust its gain as required
as
the main lens changes focal length via zooming, but it doesn't know
that
the tele or wideangle converter is there.

Now, if the camera has a menu item to tell the camera that the tele or
wideangle adapter is currently mounted, ignore what I said above - the
camera does have the required information to set the antishake system
properly.

Also, if the magnifiying device is rigidly mounted and only the camera
shakes, then the stabilization would still work correctly. This might
be the case if you are handholding the camera at the eyepiece of a
telescope or microscope, shooting through the eyepiece. But not when
the camera and other optics are both shaking.

Dave

Dave,

Thanks for your input. I had been assuming that the magnification of the
adaptor would not affect the stabilisation, and whilst I am still unsure
about exactly what happens (in that isn't the stabilisation magnified by
as much as the image?), I do accept that for best results you would need
to tell the camera that the optical chain had changed via a menu. I note
that the Panasonic FZ20, for example, has just such a menu item.

Cheers,
David

On Sun, 18 May 2008 21:31:32 GMT, "David J Taylor"

said:

Dave Martindale wrote:
"David J Taylor"
writes:
Bob Cunningham wrote:
Some cameras, like Canon G9 and Canon S5 IS, have provision
for attaching a telephoto adapter or a wide-angle adapter.

If the camera has optical image stabilization, as do those
two cameras, will that stabilization still be effective with
the added zoom adapter?

Yes.

Are you certain of that? It's not what I'd expect, though I don't
have
such a camera to test.

Here's my reasoning: Suppose the adapter is a 2X telephoto adapter.
Suppose your hand holding the camera shakes +- 1 degree in one axis.
Because of the angular magnification of the telephoto adapter, the
main
lens of the camera, looking through the adapter, sees +- 2 degrees of
angular motion, not 1 degree. The camera's acceleration sensors
detect the camera shake and move an internal lens element (or prism)
by
the appropriate amount to cancel 1 degree of shake - not 2 degrees.
To
properly cancel the larger apparent shake, the stabilization system
needs to double the gain of the system, in terms of compensation per
degree of shake motion.

The anti-shake system will automatically adjust its gain as required
as
the main lens changes focal length via zooming, but it doesn't know
that
the tele or wideangle converter is there.

Now, if the camera has a menu item to tell the camera that the tele or
wideangle adapter is currently mounted, ignore what I said above - the
camera does have the required information to set the antishake system
properly.

Also, if the magnifiying device is rigidly mounted and only the camera
shakes, then the stabilization would still work correctly. This might
be the case if you are handholding the camera at the eyepiece of a
telescope or microscope, shooting through the eyepiece. But not when
the camera and other optics are both shaking.

Dave

Dave,

Thanks for your input. I had been assuming that the magnification of the
adaptor would not affect the stabilisation, and whilst I am still unsure
about exactly what happens (in that isn't the stabilisation magnified by
as much as the image?), I do accept that for best results you would need
to tell the camera that the optical chain had changed via a menu. I note
that the Panasonic FZ20, for example, has just such a menu item.

We need to keep in mind that the stabilization technique
used on a given camera may react to vertical and horizontal
movements only, so that angular movement of the longitudinal
lens axis could not be compensated. In a Wikipedia article
about image stabilization at http://tinyurl.com/5jm42k *, it
says in part

In Nikon and Canon's implementation, it works by
using a floating lens element that is moved
orthogonally to the optical axis of the lens, using
electromagnets. The vibration signal which is
compensated for by the stabilizing lens element is
typically acquired using two piezoelectric angular
velocity sensors (often called gyroscopic sensors),
one to detect horizontal movement and the other to
detect vertical movement.

In a review of the Canon G9 at
it says

Lens-Shift type optical image stabilization system

About the S5IS, it says at
http://www.dpreview.com/news/0705/07050703canons5is.asp

Image stabilization Yes (Lens shift-type)

To counter the angular motion that DM discussed, wouldn't
the system have to rotate the lens rather than just shift
it.

Is there a way to ask someone at Canon about this?

*
http://en.wikipedia.org/wiki/Image_s..._Stabilization

Cheers,
David

On Sun, 18 May 2008 15:52:42 -0700, Bob Cunningham
said:

[...]

Is there a way to ask someone at Canon about this?

I see now that Canon offer phone and e-mail support at
http://tinyurl.com/26q3cz *

I've sent them an e-mail message about the question of image
stabilization with the 2X telephoto accessory. They say
they'll get back to me within 24 hours.

* Or
http://www.usa.canon.com/consumer/co...&modelid=15669