Since the gray card was okay: 1.) it would seem the camera is working as
expected (no auto change of exposure due to flash etc), 2.) nothing odd about
the light source. If the glass were doing something to the light, changing the
viewing angle should have a dramatic affect.
Could there be something unique about the painting itself? - more light than
expected from the painting or the glass. Some polarizers block UV? Canon
doesn't see UV?
Perhaps the ether world of OM is sending you a message ....
-jeff
that's a very challenging puzzle
-------------- Original message from Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>:
--------------
> Finally we took a black/white/gray card and put it in front of the glass
> covered painting and shot again at 1/250 and f/11. Glass area nearly
> totally washed out as before but the gray card showing as perfectly
> exposed. Another shot with my face next to the painting. Glass area
> washed out but face perfectly exposed.
>
> The conclusion would seem to be reflection from the glass. However, the
> 20D mounted on the same tripod in the same spot showed none of it. And
> how does the polarizer fit into the equation? It was clearly correcting
> the problem but, as far as I know, it shouldn't have been acting as
> anything but a 1-2/3 stop ND filter. Furthermore, since the polarizer
> wasn't expected to be acting as a polarizer, no steps were taken to
> rotate the polarizer into any particular position. Taking the A1 off
> the tripod and taking shots from different angles also didn't change
> anything. The glassed area was washed out no matter where it was shot from.
>
> I'm totally mystified. Anyone have a hypothesis about what was going on
> here?
>
> Thanks,
> Chuck Norcutt
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