Posted by
R. Ticle on
URL: https://www.es-forum.com/Camera-Motor-EMF-Cause-for-concern-tp1546119p1546145.html
Hey Bill - dang, you really know your stuff!
Well, a retailer in Toronto connected me with a technician from the
company itself, and there's also an electrical engineer or two I can
try, plus the myriad of custom magnetic shielding companies I've
contacted.
Thanks for your ongoing advice!
Best,
R.
--- In
[hidden email], "Bill Bruno" <wbruno@...> wrote:
>
> A regular tri-field won't tell direction of the field. A
buzz-stick, or if
> you
> get a tri-field with external probe can.
>
> If you can see the windings of the motor, you may be able to figure out
> direction,
> but I gather you have not opened it up?
>
> I guess there will have to be a current loop at
> the batteries.
>
> Most motors have an axle that spins, but a linear motor just uses
> an electromagnet to pull something in a straight line. With a round
> motor, the fields tend to cancel at large distances, and wrapping the
> whole thing with mu metal can work (if the motor doesn't overheat).
> Wrapping a linear motor should help, but the geometry may not lend
> itself, plus a lot of the field tends to be perpendicular. In some
> cases a thick layer of copper or aluminum can help, in other cases
> that could make the motor not work as well.
>
> I have an old SLR that you have to cock the spring. The electricity
> is only for the meters. But it needs film!
>
> Bill
>
> On Mon, Mar 10, 2008 at 5:23 PM, rticleone <rticleone@...> wrote:
>
> > Bill - can you please explain what you mean by a "linear motor", and
> > why they are difficult to shield?
> >
> > I'm not sure how to tell if the field is parallel to the back of the
> > camera. It's kind of all around it, but seems more so to near where
> > the batteries are...
> >
> >
> > R.
> >
> > --- In
[hidden email] <eSens%40yahoogroups.com>, "Bill Bruno"
> > <wbruno@> wrote:
> > >
> > > Ah- I just realized it probably has some kind of linear motor
> > > to move the mirror and shutter. These can be awful, and
> > > unfortunately not too easy to shield. If the field is parallel
> > > to the back face of the camera, try a piece of mu metal
> > > on the back, and wrap it around an inch or so on the edges.
> > > Cut out holes where needed. I have not tried holding mu-metal
> > > for long periods so you might need to put something else over it,
> > > or not keep your hand on it. But, I'm guessing you'll be lucky
> > > to get a factor of 2 or 3 improvement, which is worthwhile if
> > > you're set on this camera, but may not be enough to really
> > > make it safe.
> > >
> > > Bill
> > >
> > > On Sun, Mar 9, 2008 at 4:37 PM, rticleone <rticleone@> wrote:
> > >
> > > > Hi Bill, it does indeed have manual focus, and I've been using it,
> > > > besides, I think it's good to be able to do that - auto this,
and auto
> > > > that these days... - but it would be nice to be able to use
autofocus
> > > > for low light or fast moving objects. Thing is, every time the
> > > > shutter gets opened to take a picture, there's the same magnetic
> > > > discharge, I guess because the shutter's electronically
controlled.
> > > >
> > > > Still working on finding someone who can help. I can't imagine
it'd
> > > > be too difficult to do with the knowledge of how to open one
of these
> > > > up, I just need a willing person. I've sent out a lot of
emails, but
> > > > the weekend's just ending here, so I've got to wait a bit.
> > > >
> > > >
> > > > Best,
> > > >
> > > > R.
> > > >
> > > > --- In
[hidden email]
<eSens%40yahoogroups.com><eSens%40yahoogroups.com>, "Bill Bruno"
> > > > <wbruno@> wrote:
> > > > >
> > > > > Maybe it has a manual focus mode?
> > > > > Bill
> > > > >
> > > > > On Sat, Mar 8, 2008 at 4:13 PM, rticleone <rticleone@> wrote:
> > > > >
> > > > > > Hey Bill,
> > > > > >
> > > > > > There is a 2.5" screen on the back, but because this is an SLR
> > style
> > > > > > camera, it has to be held up to the head to "shoot", because
> > you look
> > > > > > directly through the optical viewfinder. The screen is
always off
> > > > > > when taking the picture.
> > > > > >
> > > > > > I hear you - I don't feel anything from using the camera,
and most
> > > > > > people here so far have said they probably wouldn't worry
> > about it.
> > > > > > It may not even go as high as it shows, because it's an
outdated
> > > > > > meter. But - like I said in my last reply to someone else, I'd
> > still
> > > > > > rather shield it.
> > > > > >
> > > > > > Best,
> > > > > >
> > > > > > R.
> > > > > >
> > > > > >
> > > > > > --- In
[hidden email] <eSens%40yahoogroups.com>
> > <eSens%40yahoogroups.com><eSens%40yahoogroups.com>, "Bill Bruno"
> >
> > > >
> > > > > > <wbruno@> wrote:
> > > > > > >
> > > > > > > I have heard of people reacting to cameras.
> > > > > > >
> > > > > > > What's probably important is the field inside your skull,
> > > > > > > i.e. try to put the meter where you brain is, not right up
> > > > > > > to the camera. But I would not want 3 milligauss even.
> > > > > > > Short exposure is better than long, but pulses can be bad.
> > > > > > >
> > > > > > > Having a screen on the back may be better, although a
smaller
> > > > > > > screen could be safer compared to the new big ones.
> > > > > > > Bill
> > > > > > >
> > > > > > > On Thu, Mar 6, 2008 at 6:19 PM, rticleone <rticleone@>
wrote:
> > > > > > >
> > > > > > > > I have really gotten into photography in the last couple
> > of years.
> > > > > > > > With the advent of digital cameras, I am able to take
pictures
> > > > without
> > > > > > > > dealing with developing chemicals, or the cost of many
takes
> > > > in film
> > > > > > > > to keep one shot.
> > > > > > > >
> > > > > > > > I was recently gifted (birthday gifted) a Digital SLR
> > Camera. It
> > > > > > > > works very well and takes great pictures.
> > > > > > > >
> > > > > > > > First thing I did was check it's EMF output. Very low
> > electrical
> > > > > > > > fields. That can be dealt with simply. Great!, I thought.
> > > > > > > >
> > > > > > > > Then I check it's magnetic fields. And I thought, "sh*t!".
> > Because
> > > > > > > > naturally whenever the lens focuses automatically, or the
> > shutter
> > > > > > > > opens to take a picture, there is a burst of a
magnetic field
> > > > from the
> > > > > > > > motor. I can't BELIEVE I didn't think of this before.
Gah...
> > > > > > > >
> > > > > > > > It jumps to about 35 milligauss on average (meter up
> > against the
> > > > > > > > camera, just like the face of whoever's using it -
this is the
> > > > kind
> > > > > > > > where you look through the viewfinder, it's not a point
> > and shoot
> > > > > > > > where you use the screen).
> > > > > > > >
> > > > > > > > Do I have reason to be concerned about these bursts of
> > magnetic
> > > > > > > > fields? I mean, it's not constantly against my head,
and they
> > > > last for
> > > > > > > > perhaps a second or less at a time, only when the shutter
> > fires. I
> > > > > > > > can even get away from the motor focusing the lens
most of the
> > > > time by
> > > > > > > > using manual focus and adjusting it by hand.
> > > > > > > >
> > > > > > > > Unfortunately, I can't just take this thing apart and
try and
> > > > shield
> > > > > > > > the motor from the inside, myself. There is a very
thin and
> > > > flexible
> > > > > > > > foil called Met Glas that sounds like it could be used for
> > such a
> > > > > > > > purpose, but it's the matter of getting it inside
that's the
> > > > issue.
> > > > > > > >
> > > > > > > > Maybe I can find a technician who's willing to do
it?...Hmm...
> > > > > > > >
> > > > > > > > I can theoretically shield some parts of the camera
from the
> > > > outside
> > > > > > > > with this material.
> > > > > > > >
> > > > > > > > But - what are your thoughts on these brief magnetic
fields?
> > > > > > > >
> > > > > > > > Best,
> > > > > > > >
> > > > > > > > R.
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > > >
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