RE: continued solarplate notes
I see. Indeed UV levels increase with elevation (because of thinner
atmosphere on top) but fractionally and most importantly you're located
320 miles (~ 5 degrees) North of Istanbul... I checked the UV in Montana
(Bozeman) and it was less than we had in Istanbul in the same conditions
(= open weather. Bozeman was 3, Istanbul was 4.5). Snow/ice reflect UV
quite strongly (along with water/sand) that's why you get skin burns in
the winter (or at the beach even if you're under a parasol).
It says "...The numbers are directly related to the amount of UV
radiation reaching the surface of the earth, measured in W/m2...".
Therefore - in my understanding - this should give a person the make
quite accurate exposure time predictions under sun (after some testing
and evaluating of the results). Of course, if you have a UV light
integrator than you should be able to make very accurate exposure under
sun. (Apart the fact that there may be slight contrast variations
depending on direct / indirect exposure and scattering on air. Not that
I tested this; just transferring you what I've read on this subject
BTW, see this page for info how UV Index is calculated:
From: Christina Z. Anderson [mailto:email@example.com]
Sent: Friday, April 13, 2007 6:08 PM
Subject: Re: continued solarplate notes
I never thanked you for this message....
I know that the worst sunburn I ever had was in MT. I forgot to put
sunscreen on the tops of my legs and went for a 4 hr bikeride in shorts.
Sun here is incredibly strong with the thin air, but I do not know when
begins. Our rule of thumb is sunburn outside skiing begins on Feb 1 but
before that time if you aren't wearing sunscreen you're pretty OK.
Here is a UV light meter: http://www.safesun.com/
Do you or anyone think this is an accurate device that could give
indications of outdoor UV light for photographic purposes? Or is there a
more accurate photographic one for outdoors use?
----- Original Message -----
From: "Loris Medici" <firstname.lastname@example.org>
Sent: Monday, April 09, 2007 3:54 AM
Subject: RE: continued solarplate notes
> Hi Christina,
> It depends on time (UV level peaks between 11:00AM and 01:00PM),
> season / weather and how north and south you're located...
> Currently the UV index here in Istanbul is around 4.5 at max. -> it
> can go up to 11 in mid-summer (see http://www.enka.com/weather/ - this
> particular station is located 200 yards away of my house). I guess UV
> index doesn't go above 3-4 right now in Montana; this is pretty weak.
> A definite test can be made by using a light integrator.
> -----Original Message-----
> From: Christina Z. Anderson [mailto:email@example.com]
> Sent: Monday, April 09, 2007 5:44 AM
> To: firstname.lastname@example.org
> Subject: Re: continued solarplate notes
> Considering that Mike Ware says the sun is several times more powerful
> than UVBL (anyone know the exact comparison?) this is enough proof to
> me that
> there is a quite wide range of acceptable exposure and that the ratio
> where it's at.