Re: Lens condensation question




"Floyd Davidson" <floyd@xxxxxxxxxx> wrote in message
news:87d5iru1ki.fld@xxxxxxxxxxxxx

>>>
>>>>But what I was referring to was in SoCal, if it is truly hot, it is
>>>>probably
>>>>a Santa Ana, which can produce relative humidity in the singe digits,
>>>>and if
>>>>it is damp, it is winter, and relatively cold.
>>>
>>> In fact it can happen at *any* temperature and relative humidity
>>> combination. The point in every case is that if the air touching
>>> the camera is rapidly dropped to a temperature below the dew point,
>>> it *will* result in condensation.
>>>
>>> Air with single digit relative humidity is not immune, it just
>>> has a lower dew point.

didn't say it was, but its dew point should be somewhere in the negative F
range...certainly below freezing, which is an unlikely temp to achieve when
the day time temp is around 100.
>>>
>>
>>Well, it sure happened to me, going from the rain to the inside of the
>>reception hall, my lens, and viewfinder, fogged up. Logic told me that it
>>couldn't happen, but it did.
>
> Logic should have told you that it *would* happen. That is
> *exactly* the classic case that has been explained here several
> times in great detail.

That's not what this sounded like:
"It never works in reverse. It is *always* the cooling of air to a
temperature below the dew point. The dew point changes, of course,
depending on the temperature and the relative humidity"
Admitedly, the air that is touching the lens is cooled.
--
Skip Middleton
http://www.shadowcatcherimagery.com


.

Relevant Pages

  • Re: Inadvertant IMC
    ... We have learned when the dew point and the temperature are getting ... cold saturated clear air to opaque cloud. ...
    (rec.aviation.piloting)
  • Re: Drying an unheated space: how do you measure moisture?
    ... it would seem sufficient to just air the space out ... The vent control ought to respond to ABSOLUTE humidity. ... temperature, pressure, and humidity, how can we sense those three ... I think you really need to know the temperature of the _tools_ and the dew point temperature of the ambient air. ...
    (sci.electronics.design)
  • Re: Frost
    ... Does the temperature have to be at or below freezing for frost to ... The dew on plants can freeze without the air temperature ...
    (rec.gardens)
  • Re: Frost
    ... growing plants because even though the air near the ground is heated ... I think you have this backwards, the air near the ground is cooled by radiant loss of heat in frosty conditions. ... This is because the recorded temperature is taken above ground while the temperature on the ground can be quite a few degrees lower due to radiant heat loss. ... Dew point is another way of saying humidity, it is the temperature at which, with the current moisture content, the air would reach saturation. ...
    (rec.gardens)
  • Re: humidity sensor
    ... My application is to drive a cooling fan to bring in cool air into my ... Since I have machine tools inside, dew point is important in the ... temperature, so anything more than a few degrees difference and you're ...
    (sci.electronics.basics)