MadMikeOne wrote:
Totally off topic, just noticed your location is Anchorage. When did you move?
Late summer, for better access to good medical care.
MadMikeOne wrote:
Oh I think the answer to your Extra credit question is that the meter will read higher. Not positive, though.
Why not positive. If EC=0 and EV measures 10, what will EV measure if EC is set to -2.0?
How about when EC is set to +2.0?
jaziey.g wrote:
Exposure compensation (EV) is usually used with shutter or aperture priority. Since you are controlling less you can modify brightness with EV. In manual mode u can change all 3 exposure controls: aperture, shutter, iso. No need for EV change.
EV is Exposure Value which is an
absolute measure of light. For example one meter might measure as low as -3.2 EV, another may only measure as low as -2.8 EV.
EC is Exposure Compensation, a
relative measure of light. With EC set to -1.0 the meter will read the same light as 1 stop different than it does with EC set to 0. (Extra credit: With EC set to -1.0 does the meter read higher or lower.)
IDguy wrote:
Not into Parka design. But you’ll find the better ones have adjustable vents to handle a range of heat production (exercise) and outside conditions.
Really? I never saw one with your adjustable vents. Never!
What I saw though were parkas made by Eskimo grandmothers. None had a college degree, but they actually did know what they were doing.
IDguy wrote:
... FYI I have a Masters Degree in Mechanical Engineering and aced Thermo (along with all my other College courses). ...
Okay...
If we design an Arctic parka, should there be any air flow under the parka? And if so where should there be free flow and where should there not be any flow for best protection against windchill? Lets say this is a hunting parka that might be worn for a week or two on the Arctic ice in January at temperatures down to -40 with winds of 10 to 30 MPH.
IDguy wrote:
Nope. Wind chill is a caculation of convection cooling. The only two variables in the equation are the ambient temperature and velocity. Velocity means convective cooling.
I'll have to agree with that. Velocity means heat is being carried away, and that defines convection rather than conduction. Heat is conducted to the surface, but convection removes heat from the object.
John_F wrote:
Wikipedia has has an article on Wind Chill. In it the wind chill index has units of energy per area per time. As the formula gives for 0 F and 0 mph a wind chill (labelled deg F) of 35.4 F which is warmer than the air temperature. There is something awry here. Past my pay grade.
Windchill is undefined at less than 3 MPH. The formula does not provide reasonable answers...
bpulv wrote:
Pixelmaster,
You said in your original post that you were trying to determine which lubricants to use in your camera for antarctica use. What lubricants did you arrive at and would they be of any use to those of us that are not planning for that extreme of a climate? Also, where in the camera do you replace the lubricants with the cold weather lubricants?
Replacing the standard lubricants is no longer necessary or even useful.
Today's standard lubricants are Arctic grade synthetics that are far better than what was used a few decades ago.
Dikdik wrote:
It will cool off faster, but if you leave a camera out in -40, with a 20 mph wind, and take its temperature, it will read -40 (I used -40 because C and F converge at that temperature). It will reach -40 faster.
Dik
When a warm camera from inside is taken outside into -40 ambient temperature it will cool to -40 faster if the windchill is lower. E.g., a 30 MPH wind will cool the camera faster than a 3 MPH wind.
Blaster34 wrote:
Hmmmm...if the temp is not below freezing, frostbite can't occur.
Good catch! Hypothermia, not frostbite, is what he should have said.
rook2c4 wrote:
No, Gene51 is basically correct. The only thing he got wrong is applying the term "convection" instead of "heat conduction".
How can anyone be "basically correct" and claim the difference is whether something cannot get colder than ambient. In fact windchill does not make anything colder than ambient.
That is just one "basic" flaw!
But you are correct that it is heat conduction.
Gene51 wrote:
... A camera in cold conditions will NEVER be colder than the ambient temperature, no matter how hard the wind blows. Therefore they are a not affected by the wind chill factor. The speed that warmer camera drops to ambient temp will increase, but that is not exactly wind chill - it is convection.
So you think flesh can get colder than ambient? It can't, and by your reasoning will not be affected by wind chill. NOT!
Wind chill is a measure of how fast heat is removed, and that affects any object that is not at ambient temperature already. That is not convection, it is wind chill effect.
It is astounding, or maybe shameful, that a NOAA web site makes such ignorant statements that confuse people.
And while I am quite clear about effects of windchill at 50 degrees I doubt many others are.
Incidentally I had lunch with a long time friend who has spent twice as much time in Barrow as I have. We had a good laugh over this, and are in complete agreement. It is interesting that he also has for more EMS experience than I. He rescusiated a child that was documented to have spent 40 minutes underwater.
Steve Perry wrote:
Wind chill doesn't affect cameras, only people. While wind can help pull the heat from the camera, the camera itself will never be colder than the actual, ambient air temp. Wind chill is simply how it "feels" to a person, camera's don't care.
"... can help pull the heat from the camera ..." means that wind chill absolutely does affect cameras, and in just about exactly the same way it affects humans. In either case it determines how fast terminal temperature (ambient) is reached, and does not represent a temperature lower than ambient.
I've spent the last 20 years living in Barrow Alaska. I am not guessing!
Wind chill affects the cost of heating your house, whether your car will start, when the camera battery gives up the ghost... and when your skin freezes.
One thing for the OP though, don't worry about lubrication for the camera. It has been decades now since all camera lubs are synthetic, and literally are as good can be found.
rmorrison1116 wrote:
You got the slightly blurs part correct, but not the reason for doing so. Has nothing to do with quality of lenses.
True. It relates to the spatial frequency of pixels on the sensor. With a high enough frequency an AA filter is of less value and commonly is not used.
BebuLamar wrote:
... When I open the NEF in the RAW converter the image is automatically converted to and image that is exactly same as the JPEG. ...
Not true with any RAW converter. If no changes are made only the embedded jpeg is extracted. It is almost instantanious.
If you then do make changes the raw sensor data is downloaded and appropriately converted. That takes several seconds.