In rec.photo.digital.slr-systems Floyd L. Davidson <floyd RemoveThis @apaflo.com> wrote:
> Chris Malcolm <cam RemoveThis @holyrood.ed.ac.uk> wrote:
>>In rec.photo.digital.slr-systems Floyd L. Davidson <floyd RemoveThis @apaflo.com> wrote:
>>> Chris Malcolm <cam RemoveThis @holyrood.ed.ac.uk> wrote:
>>> I'll let you do the calculations as to what that means
>>> about temperatures. Keep in mind it is spring down
>>> there, so it's how warm does it have to be to *melt*
>>> ice, not how cold does it have to be to from ice.
>>
>>You're talking about *sea* ice, Floyd.
> No, actually I'm talking about having enough sea *water*
> to operate a cruise ship and go boating in a zodiac.
> Regardless of that, my point is that we are *not*
> talking about "very serious cold" as you claimed.
We're both very obviously talking about temperatures pretty close to
zero centigrade. You've specifically said that those are the
temperatures in question, the cruise operators have said that those
are the temperatures in question, and I've said that those are the
temperatures I'm talking about. There's absolutely no point in getting
worked up about whether we ought to call a bath full of ice cubes
merely chilly, or cold, or seriously cold. It's zero centigrade, and
it stays zero centigrade until the ice has melted.
> And I do realize that it is difficult for someone, like
> yourself, who lives in a very temperate climate, to
> understand references to things which only exist in
> climates such as here in the Arctic, or the Antarctic.
It's also completely irrelevant, because as you have already pointed
out, the temperatures in question are around zero centigrade, which
I'm sure both of us have plenty of experience with.
>>According to the cruise ship
>>operators in summer in the South Shetlands the temperature hovers
>>around the freezing point of *fresh* water.
> Not exactly "very serious cold", eh?
You're giving a good impression of someone more concerned with having
an argument than making sense.
>>I'd also like to remind
> Oh, *you* are going to remind me of that I live where
> this stuff is in evidence on a *daily* basis. Really
> now...
> Stuff it lad, and start *listening* so that you can learn
> something.
If you can be bothered to shut up with your irrelevant heroic posturing
for a minute you might actyually get round to noticing my point.
>>you that the difference between a temperature which freezes ice and
>>one which melts it can be a small fraction of a degree. The very large
>>latent heat of ice makes it a very potent temperature stabiliser.
> Which is exactly why I pointed out that we are talking
> about the weather in the *spring*, as opposed to weather
> in the fall.
Please cite what temperatures you're actually talking about in terms
of numbers. I think we're talking about temperatures close to zero
centigrade, and you're trying to confuse the issue in order to posture
and sneer.
> I doubt that you can quite visualize that
> to the degree that is just blatantly obvious to someone
> who lives on the Arctic Ocean coast.
I'm quite happy to accept your basic and completely irrelevant point
that you've been a lot colder than I ever will be.
With respect to our discussion of cold cameras in the South Shetlands
at this time of year I think we're talking about temperatures of
around zero centigrade. If in fact the South Shetlands at this time of
year are even colder than that, then I'm sure you realise that the
points I've made about condensation are actually strengthened.
>>>>Under those conditions you have to wear enough
>>
>>> Under what conditions? You haven't got a clue, either
>>> about the conditions or what one would wear there.
If I haven't got a clue, why aren't you correcting me? You've spent a
great many words ranting about what a clueless temperate wimp I am,
while carefully avoiding ever mentioning what the temperatures are in
the summer in the South Shetlands. Why is that? Could it be that you
haven't a clue?
>>I know the temperature is around zero centigrade, and I know that
> That isn't what anyone would normally expect to call
> "serious".
Scientists invented numerical temperature scales in order to stop
people having this kind of silly argument about how whether a lump of
melting ice is seriously cold or not. The only thing that is relevant
to the discussion here is what the temperature actually is in the
South Shetlands at the time in question. Either you know that, or you
don't. I've told you what I think it is: around zero centigrade. I've
pointed out that if it is in fact colder then my argument is
strengthened.
So how cold is it in the South Shetlands at the time in question,
Floyd? And if you don't know, what the hell are you going on about?
>>keeping the camera warm by keeping it inside one's coat, and taking it
>>out for shots, is what is being discussed. While I haven't been to the
>>South Shetlands, I have spent many days keeping digital cameras and
>>other electronic kit warm under coats in temperatures close to
>>zero. And in some cases, until I learned how to avoid it, losing some
>>devices due to internal condensation.
> Trust that as the temperature drops it becomes
> significantly more interesting.
> You can also trust that someone who lives in Barrow gets
> more experience in one winter with cold weather living
> than you will living in Scotland in an entire life, if you
> make it to 120 years old.
So you keep saying, and I'm quite happy to accept that, especially
since it has nothing to do with the topic of this thread.
> We experience freezing temperatures an average of 324 days
> per year. Clearly the experience you get in mid winter is
> just about the same as I might have on almost any day in
> the *summer*. Except it probably *never* snows where you
> live, and it often snows in July where I live.
It snows every year where I live. Snow in June is most exceptional,
but not unknown.
>>recommendations made by the cruise operators for the kind of clothing
>>passengers should bring along suggest that it's not an unusually warm
>>kind of freezing that you get in the South Shetlands.
> An "unusually warm kind of freezing"? I'm not able to
> parse that one! What did they actually say?
I can't see the relevance of all this heroic boasting about how cold
it is where you live unless the temperature at which water freezes is
sometimes warm and sometimes cold. I apologise for using irony across
the Atlantic.
> The problem, which is what I was trying to point out
> above, is that for different people the effects are
> different. There is a *vast* difference between the way
> someone acclimated to weather in Miami Florida handles a
> windchill close to 0F and the way someone who has lived
> a few years in Barrow Alaska does.
I know that. The topic under discussion is the effect of temperature
changes on cameras, which as far as I know do not adapt to different
climates in the way that people do.
>>Many special fabrics have been devloped which
>>facilitate the wicking or transpiration of moisture while being
>>relatively wind proof.
> Look, Eskimos have known exactly how to do that for a
> few thousands of years. There isn't any need for
> "special fabrics".
<sigh> I was including the clothing used by eskimos and other northern
hunters in "special fabrics". The point, as I'm sure you realise, is
that clothing which doesn't address these special problems won't keep
you alive in those temperatures. And my specific point is that *any*
kind of clothing which does address those special problems will
necessarily have a moisture gradient as well as a temperature gradient
after having been worn for a while.
> In cold weather, wicking is generally a *bad* idea. Air
> circulation is the way to do it. Take a good look at a
> decent parka design. Open at the bottom, lots of room,
> and a hood that is an integral part of the trunk. The
> best will not have a zippered front, but that is a
> convenience that most people will want anyway; it just
> needs be done as well as possible, with flaps both
> behind it and in front, with buttons or velcro to secure
> the front one.
That's one way of solving the problem. Another way is the use of what
are sometimes called "breathable" fabrics. Old fashioned examples are
densely felted wool and very tightly woven cotton. A modern example is
Pertex. Wicking is a bad idea when used with outer clothing which is
used in the way you suggest. It's intended for use with breathable
fabrics which are not operated in that way.
> Air moves up through the parka. If it is too tight
> fitting for air movement, it will not keep you warm.
If used in the way you specified, but there's more than one way of
solving these cold weather clothing problems.
>>Pretty much any serious outdoor cold weather
>>coat will incorporate one or another kind of such technology whether
>>you are aware of it or not.
> Have you actually ever been outside in cold weather?
> Say 24 hours at -60F?
I'm quite happy to acknowledge your superior expertise in very cold
conditions. The conditions I'm trying to discuss here are the typical
summer temperatures in the South Shetlands at this time of year.
>> The result of wearing such a coat for a
>> while in cold conditions is that there comes to be a moisture gradient
>> -- more moisture inside the coat than outside it.
> Then you need to get yourself a better coat before you
> end up with a serious dose of hypothermia.
> Even in your temperate climate...
I've worn out two mountain coats in the last few decades without
getting anything close to hypothermia, even in temperatures cold
enough that if I didn't keep opening my mouth my breath froze my beard
right over my mouth in less than a minute.
I think we may be talking at cross purposes here. When I say "moisture
gradient" I'm talking about the water vapour content of the air, I'm
not talking about actual wet liquid water. It's the water vapour
content that causes condensation on cold surfaces, which is what
happens when you put a freezing camera into a warm dry atmosphere, but
one which has more water vapour in the air than can be held in air at
the temperature of the camera.
The presence of a water vapour gradient inside cold weather clothing
doesn't give anyone hypothermia, and it's an inescapable physical and
physiological consequence of wearing thermally insulating clothing
over a warm human body in the cold.
>>If you walk for half an hour in such conditions I'm pretty sure there
>>will then be enough moisture inside your coat that a camera left
>>outside for five minutes will collect a bloom of condensation on the
>>face of the lens when placed well enough inside to be warmed up by
>>proximity to your body.
> You are pretty sure, eh? The difference is that I live
> with these conditions virtually year round, and while
> you are guessing, I am not.
Will you please stop posturing about the heroically cold conditions
you live in, and try to remember the topic of this discussion, which
is the characeristic summer temperatures in the South Shetlands? I
believe that those temperatures are around zero centigrade, which
wimpishly mild temperatures I do have plenty of experience with.
>>>>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
>>
>>> That statement is what you suppose to be true. It's
>>> wrong.
>>
>>It's a well known and much discussed problem among Scottish winter
>>hill walking photographers.
> Lets see, you have a hill in Scotland that is 1409 feet
> high,
We certainly do. And thousands bigger! There's a bigger one than that
within an hour's walk from Edinburgh. It's part of what we in Scotland
call the Lowlands. Things are a little bit higher in the Highlands
> and your record cold temperature is 1 degree
> different than the _average_ temperature here in
> January...
Calm down Floyd! I quite happily accept that you're a hero with a
lifelong experience of temperatures vastly colder than I'll ever
experience. The topic under discussion here is the temperatures in the
South Shetlands in the summer -- which are around zero centigrade. I'm
quite happy to accept that to you such temperatures hardly require any
clothing at all, and can hardly even justify being called "cold", but
it does so happen that *those* are the temperatures relevant to the
OP's photographic cruise holiday.
> I expect that judging an Arctic environment by what you
> can experience in Scotland is a potentially fatal error.
Please stop posturing and start talking in terms of numbers. I
understand that the temperature in the South Shetlands in the summer
is around zero centigrade. I have plenty of experience of that kind of
temperature.
>>>>condensation when put back inside. There's a moisture gradient based
>>>>on natural transpiration as well as a heat gradient passing through
>>>>your clothing.
>>
>>> No, there is not. There is a *temperature* gradient.
>>> That means there is a gradient in the maximum amount of
>>> moisture that the air can hold, but it does not mean
>>> that somehow moisture is magically added as the air
>>> warms. It doesn't.
>>
>>It doesn't if there isn't a warm body inside the coat. I hope you
>>realise that a warm human body which is not wet with sweat still gives
>>off water vapour?
> You don't realize that trapping water vapor inside your
> coat in the manner you are describing is *deadly* around
> here.
I think you must have been looking out of the window in your school
physics classes. If it was trapped there wouldn't be a gradient. What
causes the gradient is the *movement* of the water vapour.
> In Edinburgh Scotland, yes. A wonderful place with a
> very mild temperate climate... on your coldest month
> the average low temperature is 0C.
Which as it happens is the temperature of the South Shetlands in summer.
> (The average low in
> that month here is -30C.)
Which as it happens is *not* the temperature in the South Shetlands in
the summer.
>>I've been carrying cameras around in freezing conditions nearly every
>>winter for half a century.
> Let me give you a clue: you have never been cold in your
> life, and it is obvious that you don't know much at all
> about "very extreme cold", or even mildly cold for that
> matter. You should *not* be offering your ill advised
> comments to someone traveling to Antarctica, because
> armchair exploration just does *not* provide credible
> experience.
Experience in zero centigrade conditions, which you seem happy to
admit I do have, is relevant to travel in the South Shetlands in
summer because the temperature there and then is also around zero
centigrade, is it not?
--
Chris Malcolm cam RemoveThis @infirmatics.ed.ac.uk DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]
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