Manual focus of non-full-time manual focus lenses?

I keep seeing warnings that you shouldn't manually focus the Canon lenses
that aren't Full-time Manual Focus, if they are in AF mode.

For example, in DPReview's test of the EF-S 18-55mm IS
(http://www.dpreview.com/lensreviews/..._c16/page2.asp)
they say, "The manual focusing ring rotates on autofocus, and care must be
taken not to move it accidentally with the lens set to AF, to avoid damaging
the motor."

I can imagine some damage might be done if you stop the ring from rotating
while the motor is trying to do that, but I find it hard to believe that
Canon would build a lens to sell in the hundreds of thousands, that is likey
to break in the first minutes of use from just putting on the lens cap.

Do you know of any evidence of this kind of damage?

Wilba wrote:
I keep seeing warnings that you shouldn't manually focus the Canon lenses
that aren't Full-time Manual Focus, if they are in AF mode.

For example, in DPReview's test of the EF-S 18-55mm IS
(http://www.dpreview.com/lensreviews/..._c16/page2.asp)
they say, "The manual focusing ring rotates on autofocus, and care must be
taken not to move it accidentally with the lens set to AF, to avoid damaging
the motor."

I can imagine some damage might be done if you stop the ring from rotating
while the motor is trying to do that, but I find it hard to believe that
Canon would build a lens to sell in the hundreds of thousands, that is likey
to break in the first minutes of use from just putting on the lens cap.

Do you know of any evidence of this kind of damage?


What they mean is, don't focus manually with AF engaged. Turning the
focus ring will damage the gearing between the ring and the motor. Just
putting the lens cap on is not a problem.

This kind of motor is only fitted to inexpensive lenses. The ultrasonic
ring motors fitted to most lenses, known as FTM lenses, allow touch-up
focusing after the AF has found focus, e.g. if you AF on a person, you
can touch up the focus on the eyes without disengaging the AF. If you
move the focus too far, however, the AF will kick in again, so the
touch-up range has to be within the hysteresis band so AF doesn't
reactivate.

Colin D.
** Posted from http://www.teranews.com **

Colin_D wrote:
Wilba wrote:

I keep seeing warnings that you shouldn't manually focus the Canon lenses
that aren't Full-time Manual Focus, if they are in AF mode.

For example, in DPReview's test of the EF-S 18-55mm IS
(http://www.dpreview.com/lensreviews/..._c16/page2.asp)
they say, "The manual focusing ring rotates on autofocus, and care must
be taken not to move it accidentally with the lens set to AF, to avoid
damaging the motor."

I can imagine some damage might be done if you stop the ring from
rotating while the motor is trying to do that, but I find it hard to
believe that Canon would build a lens to sell in the hundreds of
thousands, that is likey to break in the first minutes of use from just
putting on the lens cap.

Do you know of any evidence of this kind of damage?

What they mean is, don't focus manually with AF engaged.

Yeah, when DPReview says "set to AF", I believe they mean auto-focussed, not
just with the switch set to AF.

Turning the focus ring will damage the gearing between the ring and the
motor.

Yes, that's the damage I'm interested in - is there evidence?

Just putting the lens cap on is not a problem.

But a bump on the front of the lens while it's auto-focussed would be. I
find it hard to believe that lenses would be built with such a serious
weakness.

On Mon, 9 Jun 2008 21:35:26 +0800, Wilba wrote:

Just putting the lens cap on is not a problem.

But a bump on the front of the lens while it's auto-focussed would be. I
find it hard to believe that lenses would be built with such a serious
weakness.

These inexpensive lenses are probably able to withstand a
reasonable amount of turning force as well as moderate bumps. If
they would be damaged by the slightest of bumps, a huge number of
these lenses would be damaged after all these years on the market,
and if they had been, I find it hard to believe that such a design
flaw wouldn't have been widely known by now.

When DPReview clumsily said :

"The manual focusing ring rotates on autofocus, and care
must be taken not to move it accidentally with the lens set
to AF, to avoid damaging the motor."

I'm sure that they didn't mean that if you accidentally touch, or
accidentally try to rotate the ring the lens will immediately be
damaged. I'm assuming that if that attempt is made to rotate the
ring, you'll notice that there will be resistance, and that damage
won't occur unless you don't take the hint and try to use much more
than the normal amount of force. If you do that, you'll probably
end up damaging the lens's internal gears.

ASAAR wrote:
Wilba wrote:
Colin_D wrote:

Just putting the lens cap on is not a problem.

But a bump on the front of the lens while it's auto-focussed would be.
I find it hard to believe that lenses would be built with such a serious
weakness.

These inexpensive lenses are probably able to withstand a
reasonable amount of turning force as well as moderate bumps. If
they would be damaged by the slightest of bumps, a huge number of
these lenses would be damaged after all these years on the market,
and if they had been, I find it hard to believe that such a design
flaw wouldn't have been widely known by now.

Exactly. Many people say they are easy to damage, so I'm interested to hear
about those events.

I'm assuming that if that attempt is made to rotate the
ring, you'll notice that there will be resistance, and that damage
won't occur unless you don't take the hint and try to use much more
than the normal amount of force. If you do that, you'll probably
end up damaging the lens's internal gears.

OK, so a bump on the end of the lens sufficient to make it rotate could
damage it in that way. Do you know of any instances of that?

On Mon, 9 Jun 2008 23:25:00 +0800, Wilba wrote:

I'm assuming that if that attempt is made to rotate the
ring, you'll notice that there will be resistance, and that damage
won't occur unless you don't take the hint and try to use much more
than the normal amount of force. If you do that, you'll probably
end up damaging the lens's internal gears.

OK, so a bump on the end of the lens sufficient to make it rotate could
damage it in that way. Do you know of any instances of that?

No instances yet, but if you'll be kind enough to send me one of
those lenses, I'm sure that I'll soon find one. Now where'd I put
my mallet?

"Wilba" wrote in message
...
Colin_D wrote:
Wilba wrote:

I keep seeing warnings that you shouldn't manually focus the Canon
lenses that aren't Full-time Manual Focus, if they are in AF mode.

For example, in DPReview's test of the EF-S 18-55mm IS
(http://www.dpreview.com/lensreviews/..._c16/page2.asp)
they say, "The manual focusing ring rotates on autofocus, and care must
be taken not to move it accidentally with the lens set to AF, to avoid
damaging the motor."

I can imagine some damage might be done if you stop the ring from
rotating while the motor is trying to do that, but I find it hard to
believe that Canon would build a lens to sell in the hundreds of
thousands, that is likey to break in the first minutes of use from just
putting on the lens cap.

Do you know of any evidence of this kind of damage?

What they mean is, don't focus manually with AF engaged.

Yeah, when DPReview says "set to AF", I believe they mean auto-focussed,
not just with the switch set to AF.

Turning the focus ring will damage the gearing between the ring and the
motor.

Yes, that's the damage I'm interested in - is there evidence?

Just putting the lens cap on is not a problem.

But a bump on the front of the lens while it's auto-focussed would be. I
find it hard to believe that lenses would be built with such a serious
weakness.


Believe it or not, most consumer lenses are build that way.
Lenses with ring-type USM (Canon) and HSM (Sigma) are the exceptions I know
of.

OldBoy wrote:
Wilba wrote:
Colin_D wrote:
Wilba wrote:

I keep seeing warnings that you shouldn't manually focus the Canon
lenses that aren't Full-time Manual Focus, if they are in AF mode.

For example, in DPReview's test of the EF-S 18-55mm IS
(http://www.dpreview.com/lensreviews/..._c16/page2.asp)
they say, "The manual focusing ring rotates on autofocus, and care must
be taken not to move it accidentally with the lens set to AF, to avoid
damaging the motor."

I can imagine some damage might be done if you stop the ring from
rotating while the motor is trying to do that, but I find it hard to
believe that Canon would build a lens to sell in the hundreds of
thousands, that is likey to break in the first minutes of use from just
putting on the lens cap.

Do you know of any evidence of this kind of damage?

What they mean is, don't focus manually with AF engaged.

Yeah, when DPReview says "set to AF", I believe they mean auto-focussed,
not just with the switch set to AF.

Turning the focus ring will damage the gearing between the ring and the
motor.

Yes, that's the damage I'm interested in - is there evidence?

Just putting the lens cap on is not a problem.

But a bump on the front of the lens while it's auto-focussed would be. I
find it hard to believe that lenses would be built with such a serious
weakness.

Believe it or not, most consumer lenses are build that way.
Lenses with ring-type USM (Canon) and HSM (Sigma) are
the exceptions I know of.

So where are all the broken lenses?

ASAAR wrote:
Wilba wrote:
ASAAR wrote:

I'm assuming that if that attempt is made to rotate the
ring, you'll notice that there will be resistance, and that damage
won't occur unless you don't take the hint and try to use much more
than the normal amount of force. If you do that, you'll probably
end up damaging the lens's internal gears.

OK, so a bump on the end of the lens sufficient to make it rotate could
damage it in that way. Do you know of any instances of that?

No instances yet, but if you'll be kind enough to send me one of
those lenses, I'm sure that I'll soon find one. Now where'd I put
my mallet?

Umm, I'll do a bit more research first myself before I do that, thanks. :-)

For instance, I just tried to see if there is any difference between the
resistance of the focussing ring when a lens is unfocussed in AF mode, and
when it is actively focussing (AI Servo mode). I can't feel any difference.

That suggest to me that the only thing that matters is whether a lens is
switched to AF or not. In that case, putting on the lens cap is potentially
damaging.

"Wilba" wrote in message
...
OldBoy wrote:
Wilba wrote:
Colin_D wrote:
Wilba wrote:

I keep seeing warnings that you shouldn't manually focus the Canon
lenses that aren't Full-time Manual Focus, if they are in AF mode.

For example, in DPReview's test of the EF-S 18-55mm IS
(http://www.dpreview.com/lensreviews/..._c16/page2.asp)
they say, "The manual focusing ring rotates on autofocus, and care
must be taken not to move it accidentally with the lens set to AF, to
avoid damaging the motor."

I can imagine some damage might be done if you stop the ring from
rotating while the motor is trying to do that, but I find it hard to
believe that Canon would build a lens to sell in the hundreds of
thousands, that is likey to break in the first minutes of use from
just putting on the lens cap.

Do you know of any evidence of this kind of damage?

What they mean is, don't focus manually with AF engaged.

Yeah, when DPReview says "set to AF", I believe they mean auto-focussed,
not just with the switch set to AF.

Turning the focus ring will damage the gearing between the ring and the
motor.

Yes, that's the damage I'm interested in - is there evidence?

Just putting the lens cap on is not a problem.

But a bump on the front of the lens while it's auto-focussed would be. I
find it hard to believe that lenses would be built with such a serious
weakness.

Believe it or not, most consumer lenses are build that way.
Lenses with ring-type USM (Canon) and HSM (Sigma) are
the exceptions I know of.

So where are all the broken lenses?


Note the text: "I know of" :-)

Look for autofocus or back/front focus problems.