Canon T3i kit lens18-55 focus ?? If the auto focus is on can the manual focus ring be used also for focus adjustment?

hfb Loc: Northwestern Louisiana

If the auto focus is on can the manual focus ring be used also for focus adjustment?

RixPix Loc: Miami, Florida

No, not on the MKII lens. If you try you may damage the lens.

hfb Loc: Northwestern Louisiana

Thank you. I figured that was the case but can find nothing about it in the manual. Looks like a word or two would be good.

Linda From Maine Loc: Yakima, Washington

hfb wrote:

Thank you. I figured that was the case but can find nothing about it in the manual. Looks like a word or two would be good.

In related, there was a topic awhile back that asked about turning the lens after camera is shut off - in order to compact the length for putting in bag (probably was the 55-250 mm). That is also a no-no unless you set switch to manual focus first.

hfb Loc: Northwestern Louisiana

Linda From Maine wrote:

In related, there was a topic awhile back that asked about turning the lens after camera is shut off - in order to compact the length for putting in bag (probably was the 55-250 mm). That is also a no-no unless you set switch to manual focus first.

That would indicate it uses power when the camera is off. I have heard the IS also draws current when the camera is off. The more I learn about auto focus the less I turn it on. This lens is very easy to focus manually. All my experience is all manual anyway. In time my T3i will be an odd looking AE1 and I won't pick up a lot of bad habits using the T3i.

Linda From Maine Loc: Yakima, Washington

hfb wrote:

That would indicate it uses power when the camera is off. I have heard the IS also draws current when the camera is off. The more I learn about auto focus the less I turn it on. This lens is very easy to focus manually. All my experience is all manual anyway. In time my T3i will be an odd looking AE1 and I won't pick up a lot of bad habits using the T3i.

Yes, the battery will eventually drain even if never turn on the camera. Sounds like you have a good plan for future :)

DaveMM Loc: Port Elizabeth, South Africa

hfb wrote:

That would indicate it uses power when the camera is off.

That does not figure at all. The reason for Canon's warning, as I understand it, is that the motor is highly geared down to drive the focus ring, and you can easily strip the gears if you turn the focus ring with AF on, accelerating the motor.

I have actually turned the focus ring gently with AF on, without damage, but if you are at all rough or sudden in your movements and accelerate the focus motor too fast you will most likely destroy the gears.

BTW, many of the better Canon lenses do not have this drawback, and you can manually trim focus at any time during the shot.

As far as IS using power when the camera is switched off, I don't believe it. I rarely turn off IS or AF and there is no apparent discharge of the battery.

hfb Loc: Northwestern Louisiana

DaveMM wrote:

That does not figure at all. The reason for Canon'... (show quote)

With the camera off and the AF off the focus turns freely. Camera still off and the AF on, focus ring is held by the motor power. Unless the switch moves something mechanical and turns on the power.

DaveMM Loc: Port Elizabeth, South Africa

hfb wrote:

With the camera off and the AF off the focus turns freely. Camera still off and the AF on, focus ring is held by the motor power. Unless the switch moves something mechanical and turns on the power.

Not so. It is not any power from the motor, merely the sheer inertia of the it, as it turns at many times the speed of the focus ring, holding back the focus ring. If you are careful, you can bring the motor up to speed by slowly turning the focus ring. I don't recommend this, as any excess can easily lead to damage.

Edit Another demonstration of this is that the same braking effect can be felt with the lens off the camera, so there is no electricity available for the motor.

hfb Loc: Northwestern Louisiana

DaveMM wrote:

Not so. It is not any power from the motor, merely... (show quote)

OK I am wrong. A poor design at best. Is the motor physically disconnected when the switch is off?

LGilbert Loc: Earth

hfb wrote:

OK I am wrong. A poor design at best. Is the motor physically disconnected when the switch is off?

There is not wrong with the design. Either the lens internal motor or your physical efforts power the focusing mechanics. Both power sources are heavily geared down, thus, when in AF, the gearing prevents the movement of the lens just as a car in first prevents it from rolling. There is no battery drain by the lens when the camera is turned off. When you switch it to manual, the motor is unlinked from the gear train and you can adjust the focus manually without fighting (and thus damaging) the motor gear train.

More expensive lens allow manual focus to supplement the AF, but those designs are not directly geared to the motor.

DebAnn Loc: Toronto

Do you mean turning the lens on a zoom lens to its shortest length after it's turned off? I do it all the time and it has never been a problem.

Linda From Maine wrote:

In related, there was a topic awhile back that asked about turning the lens after camera is shut off - in order to compact the length for putting in bag (probably was the 55-250 mm). That is also a no-no unless you set switch to manual focus first.

hfb Loc: Northwestern Louisiana

LGilbert wrote:

There is not wrong with the design. Either the le... (show quote)

I'm a retired EE and understand motion control. There is a lot of ways to do focus control, some cheaper, some easier, some better and cheap.
I prefer to focus myself and will remember to keep it OFF.
How many axes are control in IS.?

Linda From Maine Loc: Yakima, Washington

DebAnn wrote:

Do you mean turning the lens on a zoom lens to its shortest length after it's turned off? I do it all the time and it has never been a problem.

That is what I was referring to, but am only quoting other UHH experts :)

LGilbert Loc: Earth

hfb wrote:

I prefer to focus myself and will remember to keep it OFF.
How many axes are control in IS.?

3-5, depending upon the manufacturer.