[Tfug] Way OT: optics mumbo jumbo

[Terence Rudkin]

>  Take a picture of something here on earth.  Use f16 at the ISO rating of the
>  film (funny how that works, perhaps f22 for Arizona)
Actually not so funny as the ASA/ISO is directly related to the f-stop
Something like: ev = ( f * iso / t ) * K
>.  You'll get a good
>  exposure.  Now use the same exposure settings foa a pictuer of the moon, at
>  night.  f16 and the speed set to the ISO of the film.  My guess is that
>  you'll get a fairly dark smudge.  Now go to the NASA web site and find a
>  picture of a moon rock.  It will probably look like a similar dark smudge.

You will not get a dark smudge. You'll get mid-gray.   Ansel Adams,
took a famous photo , Moonrise over  Hernandez ( archived at the
UofA).  He exposed for the moon using the Sunny 16 rule.  He knew that
would make the moon middle gray.  To make the moon white he gave the
moon  2 stops more exposure.  He exposed f8 at 1/60 for his ASA64
speed film. ( from his book  The Print, )  For those not familiar with
stops the progression is f8->f11->f16, or the sqrt(2) times the
previous stop.

TR