Photo tips for Antarctica?

TH O wrote:

> It would be so much easier if we just didn't read this nonsense and
> added all these individuals to our newsreader's killfile (aka message
> filters). It's like the Hatfields and the McCoys here.

Already filtered to be marked as read. BTW I didn't give any advice on
cold weather photography, just pointed out a troll hiding under yet
another name. I would use the 70-200 over the 70-300 because it simply
takes better pictures. A friend went to Iceland & bought that lens just
for the trip and the only other lens he had was the kit lens. He took
some great shots. I have the Nikon equivalent.
 >> Stay informed about: Photo tips for Antarctica? 

On Nov 3, 11:34 pm, Alfred Molon <alfred_mo... DeleteThis @yahoo.com> wrote:
> In article <472BBF90.5010... DeleteThis @qwest.net>, Roger N. Clark (change username
> to rnclark) says...
>
> > Everyone should be aware that this is the infamous P&S troll
> > who has been haunting these newsgroups. It constantly changes
> > its name. The headers and its style of insults give it away.
> > It is best to ignore it.
>
> Well no, this time most likely he is right.

The reason to ignore him isn't that he's wrong (he is quite
knowledgeable, but not as much as he seems to think), it's because he
is one of the people ruining the group (although he's by far not the
worst).
 >> Stay informed about: Photo tips for Antarctica? 

Robert Coe <bob DeleteThis @1776.COM> wrote:
>On Sat, 03 Nov 2007 07:53:05 -0900, floyd DeleteThis @apaflo.com (Floyd L. Davidson)
>wrote:
>: Chris Malcolm <cam DeleteThis @holyrood.ed.ac.uk> wrote:
>: >No I haven't been to Antartica, but even Scottish hills in winter are
>: >quite cold enough to demonstrate these effects.
>:
>: I'm glad you have visited someplace nice. The demonstration you got
>: on one visit doesn't seem to have been nearly as educational as
>: you'd like to think.
>
>Er... Doesn't Chris live in Scotland? He has a UK email address, and the name
>"Malcolm" is about as Scottish as it gets. ;^)

His visit was *clearly* too short to get a sharp enough
picture of what the effects actually are. Either it was
a short visit, or those Scottish hills are *not* a
suitable locatons for a demonstration.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd DeleteThis @apaflo.com
 >> Stay informed about: Photo tips for Antarctica? 

In rec.photo.digital.slr-systems Floyd L. Davidson <floyd DeleteThis @apaflo.com> wrote:
> Joell Jorgensen <jj97170976 DeleteThis @gmail.com> wrote:

>>>Second, and more importantly, taking the camera in and out of heat
>>>will cause condensation in all kinds of places you don't want it and
>>>may freeze your camera into on big block of ice. Think of what
>>>happened to glasses when you want indoors in the winter. You want in
>>>and out and in and out and the condensation will start freezing.
>>>Putting it in and out of your coat is a recipe for disaster.
>>
>>WRONG. The only time condensation happens is when the surface is COOLER than the
>>ambient air-temperatures, and only then when the temperature of that surface is
>>below the dew-point of the surrounding air. Taking the camera out of your pocket
>>just long enough to take a photo or photos will not allow the camera to cool
>>down sufficiently to cause condensation when putting it back in your pocket.
>>
>>It's obvious you've never done this and have zero experience with this. You are
>>only aping words you've read by some other moron online somewhere. Please
>>refrain from offering your foolish advice so you aren't wasting the time of
>>people like me who have to correct your annoying ignorance and misinformation.

> The fact is that what he said was correct. You didn't
> read it well.

> If you go inside and condensate forms, and then you go
> outside... it freezes. You'll endup with not just
> fogged glasses, but glasses with ice on them.

> His mistake, which you seem to have entirely missed, is
> that the above happens when you go into and out of a
> nice warm *moist* house... but inside your coat is
> usually not a moist place, because all of the air inside
> your coat was cold to start with and has no moisture
> content. Unless you are doing serious physical
> excercise and sweating profusely, there is no danger in
> taking a camera into and then out of a coat repeatedly.

Remember that the OP is talking about very serious cold,
i.e. Antartica. Under those conditions you have to wear enough
insulating clothing that there's a very large heat difference between
the air outside and inside your coat, meaning there is a very large
difference in the air's moisture holding capability. Under those
conditions you don't need to sweat profusely, or even sweat at all,
for a camera which has spent a few minutes outside the coat to acquire
condensation when put back inside. There's a moisture gradient based
on natural transpiration as well as a heat gradient passing through
your clothing. It's also quite difficult when wrapped up well enough
to stay warm while standing around in seriously cold windy conditions
to avoid sweating a bit when you start moving around.

No I haven't been to Antartica, but even Scottish hills in winter are
quite cold enough to demonstrate these effects.

--
Chris Malcolm cam DeleteThis @infirmatics.ed.ac.uk DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]
 >> Stay informed about: Photo tips for Antarctica? 

Floyd L. Davidson wrote:
> "Roger N. Clark (change username to rnclark)" <username DeleteThis @qwest.net> wrote:

>> but it won't be much different regardless of
>> the amount of air. Most of the heat transfer is not
>> conductive but radiative.
>
> You are dead wrong. The heat is mostly conductive in a
> typical place where one is going to set a camera to be
> warmed. It depends on the air around the bag being
> moved (as it cools from the bag absorbing the heat),
> thus providing a new source of heat.

This one exchange illustrates your whole rant.
You may have plenty of experience in the arctic,
but you have demonstrated you do not understand the
actual mechanisms of what is going on regarding heat
transfer. I have 30+ years working in cryogenic conditions
down to -269C (-452 F), and understand the effects, as I
have to or entire experiments would not be possible.

In many of the conditions you experience, radiative heat
transfer dominates. E.g. see:

Thermal conductivity & diffusivity FAQs
http://www.evitherm.org/default.asp?ID=676&menu1=676

A7. If I want a low thermal conductivity, which density should I choose?
Thermal conductivity for insulating materials usually
follows the expression lambda = a + b*density + c/density.
At low densities the radiation dominates, yielding a high
value of thermal conductivity.

A12. Is there an optimum density for insulation materials?
At lower densities thermal radiation will become a dominant
heat transfer mechanism

http://jen.sagepub.com/cgi/content/abstract/12/4/257
Factors Governing Heat Transfer through Closed Cell Foam Insulation
The radiation heat transfer is proportional to the square
root of the foam density and inversely proportional to the
cell diameter to the first power.

http://www.flasolar.com/physics_radiant_barriers.php
There are three modes of heat transfer: Conduction,
Convection, and Radiation (INFRA-RED). Of the three,
radiation is the primary mode; conduction and convection
are secondary and come into play only as matter
interrupts or interferes with radiant heat transfer.

http://www.astm.org/cgi-bin/SoftCart.exe/DIGITAL_LIBRARY/STP/PAGES/STP...86S.htm
Radiation Scattering Versus Radiation Absorption Effects on
Performance of Thermal Insulation Under Non-Steady-State Conditions
Radiative heat transfer through insulation can be affected
both by scattering of thermal radiation from the solid phase
of the insulation and by absorption of radiant energy within
the insulation,...
The results clearly show that if part of the heat transfer
through a medium is by direct or scattered radiation,
predictions of heat flow that are based upon conventional
conductive heat transfer analyses can be drastically in error.
In addition, it is shown that transient thermal tests on
such (scattering) media do not yield proper thermal diffusivity
values.

http://www.engineeringtoolbox.com/absolute-humidity-air-d_681.html
Humidity or moist is the water vapor present in air. Common used
terms are the Absolute, Specific and Relative Humidity.

http://srdata.nist.gov/gateway/gateway?keyword=thermal+conductivity
9 databases found for thermal conductivity.

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html
Thermal conductivity of some common materials as aluminum,
asphalt, brass, copper, steel and many more

http://www.engineeringtoolbox.com/air-properties-d_156.html
Air properties - temperature, density, specific heat,
thermal conductivity, expansion coefficient, kinematic
viscosity and Prandtl number for temperatures
between -150oC and 400oC.
 >> Stay informed about: Photo tips for Antarctica? 

"Roger N. Clark (change username to rnclark)" <username RemoveThis @qwest.net> wrote:
>Floyd L. Davidson wrote:
>> "Roger N. Clark (change username to rnclark)" <username RemoveThis @qwest.net> wrote:
>
>>> but it won't be much different regardless of
>>> the amount of air. Most of the heat transfer is not
>>> conductive but radiative.
>> You are dead wrong. The heat is mostly conductive in a
>> typical place where one is going to set a camera to be
>> warmed. It depends on the air around the bag being
>> moved (as it cools from the bag absorbing the heat),
>> thus providing a new source of heat.
>
>This one exchange illustrates your whole rant.

It demonstrates your lack of depth on this subject.

First you try to say that air is not a good insulator,
citing a "vacuum" as being better... as if that is
significant. Then you drop *all* of your previous
discussion and go for an esoteric discussion that you
hope I don't understand (and we will both grant that
very few people who read this will understand).

Of course your discussion of that one point is little
more than a "baffle 'em with bullshit" pile of
meaningless cites that do not prove your point at all!

Did you actually *read* any of those cites? Or was it
just everything that looked cool, complicated, and
overly complex when you did a Google search???

>You may have plenty of experience in the arctic,
>but you have demonstrated you do not understand the
>actual mechanisms of what is going on regarding heat
>transfer. I have 30+ years working in cryogenic conditions
>down to -269C (-452 F), and understand the effects, as I
>have to or entire experiments would not be possible.

Wonderful Roger, but the facts are that you were
demonstrating (and are again with this article) that you
simply do not understand it on a functional level. Your
experience with crygenics is useless as a basis for a
discussion of *working in* a cold climate (as opposed to
working with a few cold objects)

>In many of the conditions you experience, radiative heat
>transfer dominates. E.g. see:

In many of the conditions you experience, that may be
true. It is also irrelivant to the point that was being
made, and you can't demonstrate that it is true for the
situation I was discussing.

It is not likely to be true for what you do with the
camera that you bring in from the cold, which was in
fact what *my* point was all about.

In essense, it will be true if you wrap the camera in
almost any fairly good form of insulator, and then for
example place it where there is no air circulation.
*You* may be recommending that as an appropriate set of
actions, but I've pointed out already that it would be
counter productive to do that.

(That is not the only way to make it true, so don't get
excited and go off on a tangent. The other ways are
almost all just as illogical though...)

>Thermal conductivity & diffusivity FAQs
>http://www.evitherm.org/default.asp?ID=676&menu1=676
>
>A7. If I want a low thermal conductivity, which density should I choose?
>Thermal conductivity for insulating materials usually
>follows the expression lambda = a + b*density + c/density.
>At low densities the radiation dominates, yielding a high
>value of thermal conductivity.
>
>A12. Is there an optimum density for insulation materials?
>At lower densities thermal radiation will become a dominant
>heat transfer mechanism

You do understand what that says, right? If you use
a good insulator, the reason it will work is because it
reduces the thermal conductivity so low that radiation
is dominant.

Which is exactly why I stated that the need is to
*avoid* having an insulator, because making radiation
the dominant mechanism for heat transfer will mean a
*longer* time before the camera is sufficiently above
the dew point.

(And you claim *I* don't understand the mechanism!!!!)

>http://jen.sagepub.com/cgi/content/abstract/12/4/257
>Factors Governing Heat Transfer through Closed Cell Foam Insulation
>The radiation heat transfer is proportional to the square
>root of the foam density and inversely proportional to the
>cell diameter to the first power.

See above. Why do you cite meaningless points that in
fact disprove what you have stated? All you are doing
is saying that *if* we don't do it the way I suggested,
the it won't work the way I suggested. How amazing!

I've delete *six* (count 'em) URLs that you cited. They
all have exactly one common denominator, they mention
"thermal radiation" (except perhaps that really out in
left field URL about moisture). None of them support
what you claimed. You just posted a huge "baffle 'em
with bullshit" list of hopefully difficult to read for
most people cites in an attempt to buy credibility on
something you don't understand.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd RemoveThis @apaflo.com
 >> Stay informed about: Photo tips for Antarctica? 

Chris Malcolm wrote:
[]
> Remember that the OP is talking about very serious cold,
> i.e. Antartica. Under those conditions you have to wear enough
> insulating clothing that there's a very large heat difference between
> the air outside and inside your coat, meaning there is a very large
> difference in the air's moisture holding capability. Under those
> conditions you don't need to sweat profusely, or even sweat at all,
> for a camera which has spent a few minutes outside the coat to acquire
> condensation when put back inside. There's a moisture gradient based
> on natural transpiration as well as a heat gradient passing through
> your clothing. It's also quite difficult when wrapped up well enough
> to stay warm while standing around in seriously cold windy conditions
> to avoid sweating a bit when you start moving around.
>
> No I haven't been to Antartica, but even Scottish hills in winter are
> quite cold enough to demonstrate these effects.

So for Scottish hills in the winter, what would your recommendations be?

Thanks,
David
 >> Stay informed about: Photo tips for Antarctica? 

On Fri, 02 Nov 2007 23:40:18 -0600, "Roger N. Clark (change username to
rnclark)" <username.TakeThisOut@qwest.net> wrote:

>Floyd L. Davidson wrote:
>> "Roger N. Clark (change username to rnclark)" <username.TakeThisOut@qwest.net> wrote:
>>> Regarding cold, the idea of putting equipment in waterproof
>>> bags, like zip lock bags is good, but the idea of putting
>>> air, dry or otherwise is not a good idea.
>>
>> True.
>>
>>> It is best to
>>> minimize air, as any air can include moisture. Air has
>>> minimal insulating properties and the bag will do more
>>> than the air.
>>
>> Wrong reasons though.
>>
>> First, air is an _extremely_ good insulator. Virtually
>> *every* good form of insulation we use in clothing
>> amounts to a material that will trap and hold *air*.
>
>Not really. While air is a better insulator than some materials,
>is is nowhere near as good as a vacuum. It's all
>relative. The colder the temp differential, the larger
>air will be a factor. And air's insulating capability
>is quite dependent on the water content of the air. Dryer
>air is better.
>>
>> The problem with air in the bag is *not* the moisture it
>> might hold. If you are outside in cool air, the
>> moisture content, no matter how great or small, will not
>> be a problem when the air is *warmed* once inside a
>> building. The air can hold *more* water when warmed,
>> and hence it will *not* cause condensation.
>
>I agree.
>>
>> The problem with air in the bad when you go inside is
>> that it is indeed a good insulator, and the more air in
>> the bag the longer it will take to warm up the camera.
>
>I disagree. The mass of the air is minuscule compared
>to the mass of the camera, and a bag like a zip-lock
>plastic has better insulating power of the bag than the air.
>
>> If you squeeze as much air as possible out of the bag
>> before going inside it will reduce the time required
>> before the camera can be taken out of the bag. The one
>> thing to watch for is that you don't want to somehow
>> handle the bag in such a way that air is allowed to
>> enter it... as that would be the nice warm moist air
>> which will cool on contact and cause condensation.
>
>I agree, but it won't be much different regardless of
>the amount of air. Most of the heat transfer is not
>conductive but radiative.
>>
>> Squeeze the air out of the bag, bring it inside, and set
>> the thing in a warm spot where it will not be disturbed
>> in any way. Wait for it to warm to well above 32F (0C)
>> before removing from the bag.
>
>I agree.
>>
>>> I work with materials at cryogenic temperatures
>>> (temps below -200 C) every week, and build my own environment
>>> chambers. Antarctica is on my list of places to go.
>>> Do take a backup camera. The other problem not mentioned,
>>> which is more serious than moisture is the lubricants
>>> in the camera and lenses. They can freeze up.
>>
>> Not much of a problem for most users, simply because the
>> battery will not provide a charge long before that
>> happens. If the camera is operated from an external
>> battery pack that is kept warm, then yes that is a
>> consideration. Otherwise, not.
>
>I disagree, see below.
>>
>>> Another issue
>>> not yet mentioned is the LCD freezes, so you might lose
>>> any LCD views if the camera gets too cold.
>>
>> Years ago it would destroy some of the LCD displays to
>> even get that cold. I doubt that any of them will
>> suffer that today though. But even then you can be
>> almost 100% assured that the battery will quit before
>> the LCD does.
>
>What do you mean years ago? Search the birdsasart.com web site
>and you will see reports of LCDs failing in cold conditions.
>I've been out for hours in sub zero conditions and had
>canon 10D and 1DII LCDs "go funny." They didn't completely
>fail, but were sluggish and I could barely see an image.
>The LCDs were essentially useless, yet my battery and the
>camera kept working. I also keep spare batteries in my
>coat, and switch them out when needed.
>>
>>> You might check
>>> a photo repair shop about winterizing your gear. They remove
>>> lubricants but that increases wear, so when you get back,
>>> you might want your gear re-lubricated.
>>
>> Do *not* do that! If you have an all mechanical camera,
>> yes. If you have one operated via a battery pack that
>> will be kept warm, yes. In other words, for some (but
>> not all) professional photographers it is something that
>> might make sense. For typical battery operated cameras
>> used by amateur photographers, no.
>
>If you had a competent person who can winterize a DSLR
>I would recommend it for a really cold trip. However,
>how are probably right for the OP for this trip he
>probably won't encounter conditions that cold that winterizing
>is that critical.
>>
>> Keep in mind that the OP said he is traveling by ship,
>> with excursions via a Zodiac... He is *not* going
>> someplace where cold weather is anything near of a
>> problem!
>>
>> His problem is going to be moisture that falls from
>> those white things in the sky! Rain, mist and snow, and
>> probably a bit of spray from the boat.
>
>I agree.
>>
>> He does *not* need to know about heating cameras! He
>> needs to learn about keeping a camera *dry* in a wet
>> environment.
>
>I agree.
>>
>> Canon's do not have a good reputation...
>
>Canon haters seem to keep saying this, but I haven't
>seen any actual statistics. Do you know of any real data?
>My experience and many others I know say the opposite,
>but maybe we've been lucky.
>
>Roger


What great entertainment. The people who have never actually taken photos in
these conditions with different cameras keep doing their virtual-advice dance.

How funny can they get.

Keep going Roger Boy! .... and the rest of you virtual-photography morons. I'm
sure you'll hit on the right advice for someone some day. It's just a matter of
the odds. Like a million monkeys at the keyboard. Eventually you'll get it right
on one of them.
 >> Stay informed about: Photo tips for Antarctica? 

On Nov 4, 12:43 am, fl... DeleteThis @apaflo.com (Floyd L. Davidson) wrote:
> Robert Coe <b... DeleteThis @1776.COM> wrote:
> >On Sat, 03 Nov 2007 07:53:05 -0900, fl... DeleteThis @apaflo.com (Floyd L. Davidson)
> >wrote:
> >: Chris Malcolm <c... DeleteThis @holyrood.ed.ac.uk> wrote:
> >: >No I haven't been to Antartica, but even Scottish hills in winter are
> >: >quite cold enough to demonstrate these effects.
> >:
> >: I'm glad you have visited someplace nice. The demonstration you got
> >: on one visit doesn't seem to have been nearly as educational as
> >: you'd like to think.
>
> >Er... Doesn't Chris live in Scotland? He has a UK email address, and the name
> >"Malcolm" is about as Scottish as it gets. ;^)
>
> His visit was *clearly* too short to get a sharp enough
> picture of what the effects actually are. Either it was
> a short visit, or those Scottish hills are *not* a
> suitable locatons for a demonstration.
>

The highest point in Scotland (or, indeed, the British Isles) is Ben
Nevis, which I don't think is over 1400m (*)... And I highly doubt the
temperature there is anywhere near -30C at any point.

(*) Don't laugh. The highest point in Belgium is 700m. If the average
height of my immediate surroundings keeps following this trend, I will
soon find myself living in the middle of the atlantic.
 >> Stay informed about: Photo tips for Antarctica? 

On Sat, 03 Nov 2007 15:58:14 GMT, "David J Taylor"
<david-taylor RemoveThis @blueyonder.not-this-bit.nor-this-bit.co.uk> wrote:
: Chris Malcolm wrote:
: []
: > Remember that the OP is talking about very serious cold,
: > i.e. Antartica. Under those conditions you have to wear enough
: > insulating clothing that there's a very large heat difference between
: > the air outside and inside your coat, meaning there is a very large
: > difference in the air's moisture holding capability. Under those
: > conditions you don't need to sweat profusely, or even sweat at all,
: > for a camera which has spent a few minutes outside the coat to acquire
: > condensation when put back inside. There's a moisture gradient based
: > on natural transpiration as well as a heat gradient passing through
: > your clothing. It's also quite difficult when wrapped up well enough
: > to stay warm while standing around in seriously cold windy conditions
: > to avoid sweating a bit when you start moving around.
: >
: > No I haven't been to Antartica, but even Scottish hills in winter are
: > quite cold enough to demonstrate these effects.
:
: So for Scottish hills in the winter, what would your recommendations be?

A cozy inn with a crackling fire and a glass of single-malt whisky.
 >> Stay informed about: Photo tips for Antarctica? 

On Fri, 2 Nov 2007 19:59:23 -0400, "Joseph Meehan"
<sligoNoSPAMjoe.DeleteThis@hotmail.com> wrote:

> Stay Warm
> Have Fun
> Take Photos
>
> In that order.

That made me smile. Thanks

--
Kulvinder Singh Matharu

Website : www.metalvortex.com
Contact : www.metalvortex.com/contact/

Brain! Brain! What is brain?!
 >> Stay informed about: Photo tips for Antarctica? 

On Sat, 03 Nov 2007 07:53:05 -0900, floyd.RemoveThis@apaflo.com (Floyd L. Davidson)
wrote:
: Chris Malcolm <cam.RemoveThis@holyrood.ed.ac.uk> wrote:
: >No I haven't been to Antartica, but even Scottish hills in winter are
: >quite cold enough to demonstrate these effects.
:
: I'm glad you have visited someplace nice. The demonstration you got
: on one visit doesn't seem to have been nearly as educational as
: you'd like to think.

Er... Doesn't Chris live in Scotland? He has a UK email address, and the name
"Malcolm" is about as Scottish as it gets. ;^)
 >> Stay informed about: Photo tips for Antarctica? 

"Roger N. Clark (change username to rnclark)" <username RemoveThis @qwest.net> wrote:
>Floyd L. Davidson wrote:
>
>>> In many of the conditions you experience, radiative heat
>>> transfer dominates. E.g. see:
>> In many of the conditions you experience, that may be
>> true. It is also irrelivant to the point that was being
>> made, and you can't demonstrate that it is true for the
>> situation I was discussing.
>
>Oh come on! This started when I said when you put
>the camera in a zip-lock bag push the air out to
>minimize any moisture that is in the bag:

Which is ridiculous. Right action, wrong reason.

The moisture in the bag is simply of no consequence if
your camera is cold and you are about to enter a warmer
environment.

> > Air has
> > minimal insulating properties and the bag will do more
> > than the air.
>
>You then responded that the air was important because
>of its insulating power. I responded that it is
>negligible because radiative transfer dominates.

I did not say the air was important, I said *removing*
it is important. Your statement about radiation transfer
is without merit. It does apply *if* the camera is
surrounded by good insulation, but as I've stated the
whole idea is to *remove* the insulation.

>Try it:
>1) tape a thermometer to a camera, insulating
>it well so the thermometer reads the body temperature
>and is not affected by the air temperature.
>e.g. put it in the tripod socket.
>
>2) take it outside into the cold and let it get cold.
> in both tests in 3a and 3b make sure the cold temperature
> of the camera is the same with as close to the same total
> outside time the same.
>
>3) put it in a zip-lock bag:
>
> a) with maximum air in the bag
> b) second test with minimum air in the bag.
>
>4) bring the camera inside to a warm room.
>
>5) plot temperature versus time.
>
>You will see little difference between 3a and 3b.

Try it, and report back.

>>> A12. Is there an optimum density for insulation materials?
>>> At lower densities thermal radiation will become a dominant
>>> heat transfer mechanism
>> You do understand what that says, right? If you use
>> a good insulator, the reason it will work is because it
>> reduces the thermal conductivity so low that radiation
>> is dominant.
>
>And that is exactly the conditions experienced in the arctic,
>and the antarctic.

Roger, go read a different comic book.

>For example, thermal radiation is dominant
>because in your parka has low thermal conductivity, and

That isn't what we are talking about. You *don't* take
the camera inside the house wrapped up in your parka.

>it is working in the thermal radiation dominant regime.

How about discussing the situation we are dealing with,
rather than explaining how your bullshit applies to
something else.

>The heat loss is via scattering of thermal radiation through
>the fibers in the parka. Same with the camera in the zip-lock
>bag: the thermal conductivity of the remaining air in the bag
>and the bag itself is very low and puts it in the regime
>where radiation heat loss dominates.

Wrong. You can't have the paradox which you've just set
up, saying above that the temperature change would not
be affected by the volume of air *and* at the same time
claiming that that same air will provide insulation
sufficient to make radiation the dominate transfer
mechanism.

It either is or it is not an insulator, and in fact it is.
Hence it should be squeezed out of the bag, and that will
result in 1) more rapid worming and 2) other forms than
radiation becoming the dominant heat transfer mechanism.

It has *nothing* to do with moisture in the bag as you
claimed above. It also does not make radiation transfer
*more* significant, and indeed the idea is to make it
totally insignificant.

>There are many situations where radiative heat transfer dominates,
>e.g. feeling warmth from a campfire, feeling heat from the sun,

And I did mention that there are others, none of which
are very smart ways to warm a camera. Do *not* set it
in an oven, put it under a heat lamp, next to an open
fire or in fact just about anything that is typical of
radiant heat. It just isn't a good way to warm up a
camera!

>heat loss from your body in cold weather except when wind chill
>comes into play (then it is convective).

And indeed, a combination of convective and conductive
is what you actually do want for warming up the camera.
Ideally there would be at least a small (it doesn't take
much) amount of air flow in the area where the camera is
placed, which is a nice safe way to let the camera come
up to temperature. That means the actual heat is supplied
via convection of air around the bag. The transfer through
the bag to the camera is conductive.

>Heat loss from your
>house is mostly radiative. Heat loss from the earth at night
>(why it gets cold at night under a clear sky). Heat transfer
>from many stoves is mainly radiative. Cooking things in an oven,
>making toast, etc.

Think about it for a bit. Do you actually want to cook
your camera, and make toast out of it?

>And do you know why it stays warmer on a cloudy night?

You aren't making points with this baffle 'em with
bullshit Roger. The fact is that it doesn't necessarily
stay warmer on a cloudy night. In fact, in an area such
as where I live, for half of the year it will be
*colder* on a cloudy night!

....
>> Which is exactly why I stated that the need is to
>> *avoid* having an insulator, because making radiation
>> the dominant mechanism for heat transfer will mean a
>> *longer* time before the camera is sufficiently above
>> the dew point.
>
>Hmmm...
> > "Roger N. Clark (change username to rnclark)" <username RemoveThis @qwest.net> wrote:
> >> but it won't be much different regardless of
> >> the amount of air. Most of the heat transfer is not
> >> conductive but radiative.
>Floyd L. Davidson wrote:
> You are dead wrong. The heat is mostly conductive...

So we see I was exactly correct then, and nothing has
changed. The reason for removing the insulation is to
allow non-radiant heat transfer.

>.....Rest of rant deleted.

You are the one ranting and loading articles with
baffling bullshit. Try learning to read for one, and
sticking to relevant examples and correlations for
another. We don't really care what sort of mechanism
transfers heat into and out of a house...

>So at first you didn't seem to believe radiative forces are
>a factor, and now you do. That's good.

Can you read? I have said that the whole purpose of
removing the excess air is to avoid insulating the
camera in such a way that it would make radiation
transfer the dominant mechanism.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd RemoveThis @apaflo.com
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