Re: Exposure time im space

John Bean wrote:
On Sun, 01 Jul 2007 14:04:51 -0600, "Roger N. Clark (change
username to rnclark)" <username@xxxxxxxxx> wrote:

and if
it has an atmosphere, the absorption of sunlight through
the atmosphere.

So you think the planetary atmosphere wouldn't affect a 18%
grey card?

That's why I said "absorption of sunlight through
>> the atmosphere." In the case of the earth, absorption
is about 15% (a little more in the blue; a little
less in the red). That's about 0.2 stop.
Mars has more of a problem with scattering by red
dust in the atmosphere. Titan (moon of Saturn)
has both more absorption and scattering. The absorption
is several stops (I don't remember the exact number
off the top of my head) in the visible.

Or did you mean exposing from a grey card in space at the
same distance drom the sun as the planet - which isn't what
the OP asked.

No that is not what I meant.

Like I said earlier, piece of string until some more
parameters are defined.

Since "it is done all the time" these are well understood
and well modeled problems.

Roger
.

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