Gary Perlman
Motivated by the need to videotape software users' facial expressions,
I started to look into multiple video cameras, wall mounting brackets,
video mixers.
I was faced with a large equipment budget,
possible construction costs,
and the need to learn how to use a lot of equipment.
I don't know how it came to me,
perhaps then I used a mirror to shave in the shower,
but I thought of:
- mounting a wide-angle mirror on the
upper right of a computer monitor,
- aiming the video camera over the right shoulder
of the user so that the screen and mirror are recorded.
It worked really well!
With a $2 convex mirror the size of my hand,
mounted with a wad of packing tape or with velcro dots,
the camera can pick up a good image of the user.
With some careful adjustment of the angle of the mirror,
you can capture the user and the keyboard
and mouse, thereby replacing two extra cameras, not just one.
I usually set up the mirror in the upper right
because there is usually more of interest in the upper left.
I've used the setup for many years,
but I have a few comments and warnings:
- I usually observe in the same room as the user,
sitting in back, to the left,
so I am usually visible in the mirror.
- I use the camera's microphone to record what we all say;
even though that adds some noise, it's adequate.
- Using a standard video camera on a computer screen can
result in roll-over flicker, but it's adequate.
Often, the computer video refresh rate can be adjusted
to match the refresh rate of the camera.
- Any part of the user that sticks out will be exaggerated
in a convex mirror. This can make the user appear comical,
which is undesirable.
- Getting good lighting on the user is difficult
because the screen is a light source.
My best balance has been with well lit rooms,
not with a spot light on the user's face.
- It is important to get a generous border around the subjects of interest,
and fine grained detail is usually not needed for the screen
(the usability team know most of what is on the screen).
- I use manual focus because autofocus can get confused.
- I turn off automatic image stabilization to get better detail.