Photographing the screen

[Joe Cychosz]

Film:
   I use Kodak 100 print film for prints and Ektachrome 100 (Ektachrome
64 is no longer available) for slides.
I have not tried Ektar 125 yet.  This is probably the best print film
to use as it has an incrediable grain density and excellent color.  The
exposure settings will have to adjusted slightly.  The next roll I shoot
will be Ektar 125.

Setup:
   This is the longest and most crucial step.  It is important to get the
lens as perpendicular as possible to the screen.  Things to watch for are
monitors which tilt (like Suns or SGIs).  I also try to get the lens as
close as possible to the screen and still be able to focus. This helps
reduce the effects of the curvature of the screen.  For a 70-210mm Macro
Nikon this is about 2 ft at 70mm.  This contradicts what one might think
in that one would expect the flattest photo to appear by getting as far
away as possible and shooting with as long of a lens as possible.  The
problem is in the distoration in the lens system at 210mm.  Keep in mind
that a macro lens works on a series of approximations.  What results
is concave pillowing which is oppisite of the convex pillowing caused by
the curvature of the screen.  The optimal flat picture occurs when the
convexed pillowing of the screen is balanced with the concaved pillowing of
the distortion in the lens system.  Since I do not have a straight 200mm
lens, I have not been able to study and measure the distortion in the
macro.

   One final note: I tend to shoot images that are either 640x480 or 512x
512 off of the SGI.  I have shot full screen images, but the curvature of
the screen gets a bit difficult to control, especially with the 70-210
lens problems.

Exposure:
   I use a 1/2 second exposure at f8 with half a stop added in.  To bracket
the exposure I also shoot a f5.6 and a f11 exposure.  With 100 speed film
the exposure can be fairly forgiving.  That is to say, you'll get a
reasonable picture as long as the exposure and f-stop are within reason.
Never shoot faster than the refresh rate of the monitor, 1/60th.  A wide
black bar will appear on the screen.  This even goes for taking pictures
of monitors sitting in rooms.  If you do you will endup with black bars on
the screen.  For room shots I use 1/8 second or longer.

   I have shot 1 second exposures at f8 and have had similar results.
Again, 100 speed film is pretty forgiving.

   I have found the exposue metering systems in cameras to unreliable when
determining the exposue.  This is especially true when shooting vector
displays.  Also, you want to avoid full white areas such as menu areas
and the like.  Change them to a 70 - 80% grey.  The pictures will look
much nicer when printed.

Processing:
   For prints I usually tell the people that process my film that the
roll contains computer graphics.  Many film printers are computered
controlled and are setup for printing people, sky, grass, trees and other
things which you would find in normal photos.  These printers usually
lose it when the get a picture with lots of black and fully saturated
colors.  Vectors are the hardest to process.

   I use a Noritsu and a Fuji machine for my processing.  Usually
one or two units of density must be added (i.e., +1, +2) for computer
graphics shots.  The process you are going through is to balance the
quality of the color with the quality of black.  If you don't do this
you will end up with brown instead of black.  The Noritsu and Fuji will
will print on the back of the photo what settings were used.  So if you
do reprints bring the old photo in so the processor can see what settings
they used last time.  Examples follow below:

	Noritsu:
		896 45 N N N 6 2

		896   = Sequence number
		 45   = Film code (45 = Kodak 100)
		N N N = Yellow, Magenta, Cyan print levels.
			N = neutral, there will be numbers -1, +1, etc.
			for non-neutral settings.
		  6   = Density setting.
		  2   = Ignore.

	Fuji:
		79  010005 28 +01
		+0 -01+02 NN    -5  0

		79    = Sequence number.
		010005= Film/vendor/speed code (Kodak 100)
			010205 for Kodak 200 Gold
		28    = Daily density setting, results from calibration.
		+01   = Density setting.
		+0 -01+02 = Cyan, Magenta, Yellow print leves.
			+0 = neutral.
		NN    = Ignore.
		-5  0 = Ignore.

   One other problem the film processing machines have is alignment.
Lets say you are shooting pictures of some square 512x512 images.
The film processor will more than likely assume that the left edge
of the image is the left edge of the picture.  I will not center it for
you.  This will also happen with slides.  To solve this problem two
things can be done.  One: shoot a few fully exposed pictures at the
beginning of the roll so the machine can set where the left edge is
for the rest of the roll.  Or two: us an alignment background pattern
like I do.  This looks something like this:


                ----------------------------------
                !               !                !
                !               !                !
                !       -----------------        !
                !       !               !        !
                !       !               !        !
                !-------! Image         !        !
                !       !               !        !
                !       !               !--------!
                !       !               !        !
                !       -----------------        !
                !                 !              !
                ----------------------------------

I am in the process of working on a calibration image which will help
the process people make there settings.  I am also working on reducing
the yellow edges which appear (especially at red and green boundries).
I don't expect to have any of this done sometime soon though.