DSLR vs P&S a replay of Film vs Digital?

In article , William
Graham wrote:

muscle memory also plays a role. i know exactly how far to turn the
zoom ring to get to where i need, whereas there's a latency with a
fly-by-wire ring, and with two buttons, it is simply impossible.

Yes. - My gut instinct tells me that auto zoom mechanisms are only useful
where the machine is too big for you to conveniently get your hands around
it to turn it manually, so you have to have it driven automatically.

you mean like this?

http://www.sigma-photo.co.jp/english/news/200_500_28.htm

it has built in zoom and focus motors including its own power supply
for them. not that it is actually shipping or anything -- sigma
produces more vaporware than anyone else.

Otherwise, there is nothing to be gained by driving it automatically.....It
won't be better than manual operation. Obviously, Mt. Palomar has to be
zoomed automatically, but my Nikkors will operate most efficiently if I zoom
them by hand.

actually pentax had a few slr lenses with power zoom and they didn't
sell that well.

http://www.mosphotos.com/PentaxLensPowerZoom.html

On Mon, 19 Nov 2007 14:33:25 -0800, "William Graham"
wrote in :

"John Navas" wrote in message
.. .

With all due respect, it's quite possible to have a zoom system with
little or no overshoot, especially since zoom is less critical than
focus. The experienced user anticipates the desired point when using
the control. With distance (not just direction and/or speed) control,
the experienced user can even signal a final point almost instantly,
with speed of response limited only by motor power.

But you have to define the right point to the machine......You can tell the
camera that you want any given focal length in millimeters, but then you
would have to know what that figure is, and if you don't know that, but are
just zooming to get a given object to fill 2/3 of your frame, (for example)
then how are you going to translate that into machine language? IOW, even if
you know where you want it to be, you have to use "machine speak" in order
to tell the camera where that place is. Otherwise, the machine will have to
slew slow enough for you to be able to stop it at the right place......I
think that, like your mouse, you should be able to adjust the speed in
software somewhere to find a point where you are comfortable with it, and
this point will vary according to the photographers ability. But the camera
can never know in advance exactly how far you intend to go as it does with
auto focusing, because the final point can't be defined in machine language.

Only a crude system would have to depend on a slow slew rate. It's
quite easy to design a fast active servo system with a simple and
effective control input. One possible way is the same as manual zoom.
Someone experienced with manual zoom moves the zoom control to the
approximate desired point by experience, limited by the speed with which
elements can be shifted by the manual zoom control. Turn that control
into fly by wire and it can be moved into position faster, and sensed
continuously in terms of distance and direction by the servo control,
which can accelerate and decelerate the zoom motor on an optimum
acceleration profile, aided by less mass and mechanics due to the lack
of manual zoom connection. At the same time it can automatically
compensate for beneficial nonlinearity (undesirable in a manual system)
and for focus shift (present in even the best zoom optics). Such fast
active servo systems are now very well-understood (think disk drives,
and the difference between slow obsolete steppers and current high-speed
servos). Even more sophisticated systems could add control rate
sensing, eye movement, object sensing, etc.

Moving a mouse is analogous once you're comfortable with it, and are not
moving the mouse pointer by watching its entire movement. (You can
easily tell the difference between someone experienced with a mouse, and
someone still feeling it out.) You rapidly move the mouse to the
approximate desired point, and then fine tune from screen position once
you get there, aided by multiple speeds and an acceleration profile.
Zoom needs less precision, and so can be even faster.

A mechanical zoom system is really no different, except it's limited to
a single speed and no acceleration, and simply can't compete with a
sophisticated servo system. The only reason that's not already obvious
is that current power zoom systems are relatively primitive -- the
two-speed zoom on my Panasonic FZ8 is only a modest step up, and even so
is still fairly new.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

In article , John Navas
wrote:

Moving a mouse is analogous once you're comfortable with it, and are not
moving the mouse pointer by watching its entire movement. (You can
easily tell the difference between someone experienced with a mouse, and
someone still feeling it out.) You rapidly move the mouse to the
approximate desired point, and then fine tune from screen position once
you get there, aided by multiple speeds and an acceleration profile.
Zoom needs less precision, and so can be even faster.

moving a mouse is analogous to a mechanical linkage. the trackpoint
control on a thinkpad is analogous to a motorized zoom.

http://www-307.ibm.com/pc/support/site.wss/VLAR-443LTU.html

A mechanical zoom system is really no different, except it's limited to
a single speed and no acceleration,

nonsense. mechanical zoom can move at any speed the user wants.

and simply can't compete with a
sophisticated servo system.

it can and it does.

The only reason that's not already obvious
is that current power zoom systems are relatively primitive

indeed they are. maybe one day in the future they'll be better. right
now, no.

On Mon, 19 Nov 2007 15:31:27 -0800, "William Graham"
wrote in :

No one is questioning the speed capability of an auto-zooming mechanism.
What I am questioning is the need for an automatic system if the lens is
small enough to be operated directly by hand, since the correct end point is
subjective and not easily communicated to the camera.

It is easily communicated to the camera. (Just because you can't think
how to do it doesn't mean it can't be done.)

There is no substitute
for direct positioning by the hand of the photographer, who's compositional
decisions can't be communicated to any automatic mechanism.

Control is of course needed in all control systems, but does not have to
be "direct", which can actually be less effective than accelerated
systems.

Only if the lens
is too big and heavy to be moved easily by hand would an auto driving
mechanism be more useful than directly positioning the lens by the hand of
the one that is making the decision based on his sense of composition.

There can actually be a number of advantages to an advanced servo system
over direct positioning -- see my prior response.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Mon, 19 Nov 2007 14:52:59 -0800, nospam wrote
in :

In article , William
Graham wrote:

The problem is that the mechanism doesn't know where the final resting zoom
point is going to be. With auto focusing, the camera can calculate how far
it has to go to reach the "in focus" point, and can go there in one hell of
a hurry. But zooming is a compositional thing, and so the right place is
subjective, and is at the discretion of the photographer, so the auto
mechanism has to be slow enough so anyone can handle the speed. Because of
this, I doubt if it will ever be fast enough for most photographers........

muscle memory also plays a role. i know exactly how far to turn the
zoom ring to get to where i need, whereas there's a latency with a
fly-by-wire ring, and with two buttons, it is simply impossible.

Latency is simply an artifact of current crude zoom systems.
Advanced servo systems do not have noticeable latency.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Mon, 19 Nov 2007 15:08:26 -0800, "William Graham"
wrote in :

"nospam" wrote in message
.. .

muscle memory also plays a role. i know exactly how far to turn the
zoom ring to get to where i need, whereas there's a latency with a
fly-by-wire ring, and with two buttons, it is simply impossible.

Yes. - My gut instinct tells me that auto zoom mechanisms are only useful
where the machine is too big for you to conveniently get your hands around
it to turn it manually, so you have to have it driven automatically.
Otherwise, there is nothing to be gained by driving it automatically.....It
won't be better than manual operation. Obviously, Mt. Palomar has to be
zoomed automatically, but my Nikkors will operate most efficiently if I zoom
them by hand.

Your gut is not correct -- see my prior response on fast servo control.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Mon, 19 Nov 2007 14:38:47 -0800, "William Graham"
wrote in :

"John Navas" wrote in message
.. .

The artificial intelligence and imaging guys are way beyond that, and
still aren't even remotely close to autonomy. The basic problem is that
science is unpredictable. If it were predictable, then there'd be no
point in going.

Yeah.....And they have to be careful of just how autonomous they make the
machine.....If they give it too much leeway, it might decide to bomb the
White House with 400 mm f/2.8 lenses......

Or crude power zoom mechanisms.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Mon, 19 Nov 2007 15:25:48 -0800, SMS ???• ?
wrote in
:

Neil Harrington wrote:

Manual zoom is great, especially if it's really manual zoom and not just a
zoom ring that controls zoom by wire. It's probably the best thing about the
old Minolta Dimage 7 family of cameras, a few of which I still own.

The mechanical zoom on the Fuji S6000fd was wonderful, but unfortunately
it got removed on the S8000fd. The manual zoom is an order of magnitude
(at least) faster than the motorized zoom.

You've got no actual experience -- you're just guessing, and thus not
surprisingly way off the mark (as usual on all three counts).

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Mon, 19 Nov 2007 16:21:06 -0800, nospam wrote
in :

In article , John Navas
wrote:

Moving a mouse is analogous once you're comfortable with it, and are not
moving the mouse pointer by watching its entire movement. (You can
easily tell the difference between someone experienced with a mouse, and
someone still feeling it out.) You rapidly move the mouse to the
approximate desired point, and then fine tune from screen position once
you get there, aided by multiple speeds and an acceleration profile.
Zoom needs less precision, and so can be even faster.

moving a mouse is analogous to a mechanical linkage. ...

Only an ancient mouse -- a current mouse is actually a multi-speed
system with acceleration profile that's not at all analogous to
mechanical linkage.

A mechanical zoom system is really no different, except it's limited to
a single speed and no acceleration,

nonsense. mechanical zoom can move at any speed the user wants.

Mechanical zoom is only single speed, has no acceleration, and is
limited by mass, friction, and hand-eye coordination.

and simply can't compete with a
sophisticated servo system.

it can and it does.

You're badly misinformed about fast servo systems.

The only reason that's not already obvious
is that current power zoom systems are relatively primitive

indeed they are. maybe one day in the future they'll be better. right
now, no.

They're actually pretty good, especially considering their relatively
primitive design, and will undoubtedly continue to get better.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Mon, 19 Nov 2007 14:37:04 -0800, SMS ???• ?
wrote in
:

Neil Harrington wrote:

Your header still says Forte Agent 4.1/32.1088. Jump up and down and flap
your lip all you like, you're too ignorant to do anything but the easy stuff
that most ten-year-olds can do, as I said.

The problem is that other people are also using Forte Agent, so
filtering based on " in the message ID would cause the loss of
some worthwhile content as well.

I'm still looking for a newsgroup reader that downloads not only the
headers, but the bodies of all the posts as well, then filters based on
keywords in the body. Since he uses similar language no matter what his
name is, it would be pretty easy to filter that way.

Your ignorance is showing (again) -- that's actually quite easy to do.
I've posted one such method a number of times.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)