Taking pictures from the screen
Some remarks that came to my mind reading this message. I only quote the
parts that are important for my followup.
More important than the photography is the preparation of the picture on
the screen. Use a dark background. Use bright colors to render the model.
Adjust the brightness, line thickness and contrast in such a way that
features are clearly visible from a distance. Turn out the room light
I think it is absolutely impossible to take any photograph without the
room lights off. Later you will talk about exposures of about 1 second: try
taking a one second photograph in a lit room.... And: Lock The Door!
Compose the picture using a tripod at a convenient distance, say a little
farther than the minimum focal distance of your lens. With a zoom lens,
you have more flexibility on the tripod position. Make sure that all of
the model is covered and all of the picture frame is filled.
If you take a picture from a very close distance, you will see a deformation
on the photograph, because no screen is really flat. We mostly use a distance
of about 2.5 metres.
Exposure time: Unfortunately, you cannot use the auto-exposure feature,
no matter how sophisticated your camera is. This is because the light is
not distributed uniformly on the screen. You may need to experiment.
Use bracketing, i.e., shoot the same picture at different exposure levels
and choose the best one after developing. I would try a quarter, half
and a full second.
We have the experience that an averaging measurement of the light intensity,
in combination with the 'bracketing' works fine. In general that will indeed
be exposure times in this range.
In general you have to adjust the screen to different brightness and
contrast values when you are taking photographs than you would
normally have done.
A final word of wisdom: If your picture does not turn out well, you
cannot blame me.
That holds for me too.
Rob W.W. Hooft, Department of crystal and structural chemistry
Bijvoet Center for Biomolecular Research, University of Utrecht
The Netherlands ===== hooft;at;chem.ruu.nl (hooft;at;hutruu54.bitnet)