[AG-TECH] Lights, camera, question

Wenjun Liu wliu at mcs.anl.gov
Fri Sep 7 14:25:13 CDT 2001


>From my recent practice of installing an AG node, my thousands of
picture-taking experiences over the years, and my personal interests, here
are my two cents:

These days most cameras have advanced metering system that is linked to the
focusing points those cameras use. For most of the time, an integration of
exposure and focus ensures clarity and contrast in most images the camera
captures. When metering subjects against very dark or very bright
backgrounds, most cameras use partial-area metering that measures only, for
example, 10 percent of the area around the chosen focusing point. This will
provides accurate image exposures when dealing with shadows or highlights.
However, as you zoom out, more backgrounds and subjects are included in
focusing area. The camera has to meter all of them and calculate one
exposure measure, usually an average between the brightest and darkest. For
that purpose, making the walls, couches, tables, etc. as much the same color
as possible (not merely paint the walls) will help, especially when you zoom
out to capture all of them. In addition, I found direct lights on human
faces almost always ruin the picture, especially combined with backgrounds:
either too bright or too dark. Using some reflection lighting may help: e.g.
a whiteboard to reflect light back to human faces usually will give you
better images of human faces. Sometimes the ceiling will be your best
reflecting source. Pointing a light (from somewhere in the room at certain
angle) to the ceiling usually will give you softer images of human faces.
But you have to test the light angles, taking into consideration of room
design, seating arrangement, and your camera positions. It should be lots of
fun to test the best lights and camera positions arrangement, though people
usually do not bother that much on these issues.


----- Original Message -----
From: "David Minor" <dminor at salud.unm.edu>
To: <ag-tech at mcs.anl.gov>
Sent: Friday, September 07, 2001 12:10 PM
Subject: [AG-TECH] Lights, camera, question

> So we're doing some final prep work on our room, and  I wanted to buzz a
few questions to people to get their opinions and experiences.
> Initially the room was pretty standard, with white walls and overhead
flourescents. This caused some issues with our cameras (Sony Pan and Tilts),
namely that the cameras "saw" a lot of the white walls and tried to
compensate, causing people's faces and clothes to be shaded oddly (usually
too dark).
> On the advice of several people we painted our walls a darker color - sort
of a plum shade. This seems to help tremendously. We also had a lighting
expert come in and spec new lights. His recommendation was to install much
higher speed flourescents, and have them installed at an angle facing away
from the projection screen. This we have done and it also helped the room
> But - we are still less than pleased with our results - especially
comparing it to how some of the other rooms out there look. Our primary
problem is that when zoomed out as wide as possible (to see all audience
members) the image quality is pretty bad - the whites and light colors
especially are way too overpowering (most people's faces are washed out for
> So, to my question: what are people's thoughts about lighting in rooms? Is
it something that they have worked on or changed and what have been the
results. Alternatively, what about cameras? Is anyone using anything else
that they think works better? Are we bumping up against the limitation of
the optics or could it be soomething else?
> Thanks in advance for any input!
> david.

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