> All of which doesn't change the fact that the level of UV absorption isn't
>
> nearly enough to make it safe to look at the sun through the glass.
> Hersch
>
Quite true. Uh, what was the original question? :-) Just kidding - time
to let this topic die.
Alan Tyson wrote:
>> All glasses strongly absorb UV radiation
>
>
> Oh good. That's what I was trying to tell people. Thanks.
>
> We could also mention the effect of path length, i.e., a
> window pane vs a 14-element lens.
>
> Alan T
>
I'm convinced some camera lenses are made of 14 eleme
All of which doesn't change the fact that the level of UV absorption isn't
nearly enough to make it safe to look at the sun through the glass.
Hersch
At 05:59 AM 02/06/2001 -0800, you wrote:
> > Shough, Dean wrote:
> >
> > >> From a prctical point of view, I seriously doubt that glass absorbs a
> >All glasses strongly absorb UV radiation
>
> Oh good. That's what I was trying to tell people. Thanks.
>
Sorry, but I did not mean to imply that glass would absorb all wavelengths
of UV radiation.
UV light can range from 5 to 400 nm. The various glasses tend to start
absorbing _somewhere_
;[EMAIL PROTECTED]>
Sent: Tuesday, February 06, 2001 1:59 PM
Subject: RE: filmscanners: Re: looking at the Sun
> Shough, Dean wrote:
>
> >> From a prctical point of view, I seriously doubt that glass absorbs a
> heck
> >> of lot of UV, certainly not over a long term.
> >>
> >
> >
> > Correct. Most glass readily transmits near UV quite well. For example,
> a
> > very common optical glass, BK7 transmit
Shough, Dean wrote:
>> From a prctical point of view, I seriously doubt that glass absorbs a heck
>> of lot of UV, certainly not over a long term.
>>
>
>
> Correct. Most glass readily transmits near UV quite well. For example, a
> very common optical glass, BK7 transmits 80% of light at 34
> From a prctical point of view, I seriously doubt that glass absorbs a heck
> of lot of UV, certainly not over a long term.
>
Correct. Most glass readily transmits near UV quite well. For example, a
very common optical glass, BK7 transmits 80% of light at 340 nm and 5% at
300 nm. This is typi
> Infra-red is on the other end of the light spectrum and is of very low
> energy per photon compared even to light. It is manifested to us as heat.
> How is this dangerous?
>
Have you ever taken a magnifying glass and used it to burn a leaf? Replace
the magnifying glass with the lens in your ey
> Most glasses absorb UV much more strongly than IR. Most of
> the materials used for sun viewing and photography (eclipse
> goggles) have a (log10) density of 5-8 for UV and visible,
> and less than 5 for IR.
>
> The worst of the lot is fogged colour negative film, which
> is fine in the UV & v
TECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, February 04, 2001 10:13 PM
Subject: RE: filmscanners: Re: looking at the Sun
> Infra-red is on the other end of the light spectrum and is
of very low
> energy per photon compared even to light. It is manifested
to us as heat.
> How is this dangerous?
negabs01.gif
gt;From: "Alan Tyson" <[EMAIL PROTECTED]>
>To: <[EMAIL PROTECTED]>
>Subject: Re: filmscanners: Re: looking at the Sun
>Date: Sun, Feb 4, 2001, 11:52 AM
(snip)
> Most glasses absorb UV much more strongly than IR. Most of
> the materials used for sun viewing and photog
001 11:53 AM
> To: [EMAIL PROTECTED]
> Subject: Re: filmscanners: Re: looking at the Sun
>
>
> Infrared is also a serious, if not worse, hazard. Glass is
> fairly transparent to it, as shown by greenhouses, passive
> solar panels, the burning of holes with magnifying glasses,
&
ASA's web site has lots on this under solar eclipses.
Regards,
Alan T
- Original Message -
From: Laurie Solomon <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, February 04, 2001 5:13 PM
Subject: RE: filmscanners: Re: looking at the Sun
> True, but only a v
periods ( Here I am speculating since I do not know if the harmful effects
are cumulative).
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Berry Ives
Sent: Sunday, February 04, 2001 9:22 AM
To: [EMAIL PROTECTED]
Subject: Re: filmscanners: Re: looking at the
At 21:16 03-02-01 -0800, you wrote:
>I'm sure others will chime in on this one, but I can't let that advice go
>unanswered. Just because the image in an SLR viewfinder is replected up
>through a pentaprism and a ground glass screen is no reason for
>complaisance about looking at the sun with su
on 2/3/01 11:50 PM, Laurie Solomon at [EMAIL PROTECTED] wrote:
> I concur with you Hersch but would add that the danger is not from the
> brightness of the light but from the ultraviolet light rays that the sun
> emits and which are not screened out all that much by one-way mirrors and
> pentapri
I concur with you Hersch but would add that the danger is not from the
brightness of the light but from the ultraviolet light rays that the sun
emits and which are not screened out all that much by one-way mirrors and
pentaprisms.
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL
The shots I mentioned where I do do this are always extreme wide angle which
is no worse than looking up in the sky with the sun at the extreme periphery
of our vision. Still, extreme care should be exercised, as you say. Usually
what I do is compose with the sun just out of reach then shift sligh
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