That's a "bump shield" used for filming the IMAX movie A Beautiful Planet.
According to IMAX, their desire to film from aboard the Cupola forced
them to design an "exclusive bump shield made of a space-rated clear
material" that was "equipped with sliding doors" to allow the cameras
to have the clearest possible views. The shields were flown into space
specially for A Beautiful Planet.
IMAX used modified Canon C500 digital cinema cameras since the Shuttle was not available to manifest the large, heavy IMAX cameras and film.
Camera type source
Reid Wiseman with the camera.
Former astronaut Marsha Ivins, bearer of legendary space hair, and IMAX consultant talks about the bump shield
Marsha, I heard that you had to rework the plexi window that the
Astronauts were shooting through. Can you tell us about that, please?
MARSHA: We started building the ISS in 2000, and we carried each
module to be added to the ISS in the cargo bay of the Shuttle, one at
a time. The Cupola was put on board in 2010. The Cupola is a module
that consists of 7 windows—six circumferential and one nadir (center)
window facing Earth. It has nice, lovely, optical glass that NASA then
covered with cheap, non-optical Plexiglas in order to protect the real
glass. Over the years that the module has been in space, the Plexiglas
covers have been bumped and scratched. Because it’s such a so[ft]
material, it is easily scratched and difficult to clean. When there’s
dirt and grime on it, and then you try to clean it, you basically
scratch it more. Shooting any picture through one of those windows
reveals all the scratches.
So, in order to save IMAX an arm and a leg in post-production costs
trying to remove scratches digitally—many of which they probably
couldn’t have taken out anyway—we asked NASA if it would be possible
to design and fly a new protection for the windows that allows you
access to the real window for shooting. We had the NASA engineers
basically design it: they told us the material, the thickness, the
kind of fasteners that would be needed, what the opening should be,
and so on. We had the thermal people bless it. We had everybody who
would have done the NASA design get involved, but then we had IMAX
build it. We had it certified as a piece of payload hardware, which
was how we flew the cameras. We had it manifested to launch. Then we
got the crew some time for installation. It’s still in place. They
continue shooting regular NASA stuff through it now.
Source - same as Reid Wiseman picture