[Dragaera] The Enclouding

[Jerry Friedman]

--- On Sat, 10/11/08, Michael Wojcik <mwojcik at newsguy.com> wrote:

> From: Michael Wojcik <mwojcik at newsguy.com>
> Subject: Re: [Dragaera] The Enclouding
> To: dragaera at lists.dragaera.info
> Date: Saturday, October 11, 2008, 10:29 AM
> Alexx Kay wrote:
> > 
> > OTOH, that passage has other interesting features; it
> implies strongly
> > that while Castle Black is (at that time) hidden from
> view from below by
> > the overcast, people inside CB could still see the
> ground.  Is there some sort of polarization?
> 
> There needn't be. The obscuring effect of a translucent
> layer is more
> pronounced the further the observer is from the layer, and
> it's more
> pronounced for viewers in the region with greater ambient
> light. If
> you stand in the edge of a fogbank, you can often see out
> perfectly
> clearly, while remaining more or less obscured to outside
> viewers.

Agreed so far.

> In a similar vein, consider someone wearing a fencing mask
> - they can
> see out quite clearly, but it's hard to see his or her
> face. That's
> partly because the layer diffracts both incident and
> reflected light,
> so the light the fencer sees by is diffracted once, but the
> light the
> audience sees reflected from the fencer's face is
> diffracted twice.
> But it's also because the fencer is much closer to the
> diffraction
> grating, so whatever the angle of diffraction, the rays
> reaching the
> fencer's eyes have diverged much less than those
> reaching the eyes of the audience.

I don't think there's much diffraction going on in a
fencing mask.  The spacing is too big.  (I admit it's
been twenty years or so since I last saw anyone in a
fencing mask, and longer since the two times I've
worn one.)  What's going on is that the mask shades
the fencer's face while the rest of the room (including
the mask) is well lit, and the tiny visible bits of
the fencer's face are hard to resolve from the bits
of mesh next to them.

Jerry Friedman