🚀 go-pugleaf

In article <4783@ecsvax.UUCP> khj@ecsvax.UUCP (Kenneth H. Jacker) writes:
>
>	I need to make color slides of a Mac II screen.  My
>system uses Apple's High-Res RGB monitor.
>
>	Any suggestions regarding film type, shutter speed,
>aperture, and/or exposure time?
>

I've photographed a few CRTs.  While I can't give you exact exposure info
I can offer a few helpful hints.

1)	The room must be DARK.  Completely.  Any light spilling onto the
	screen will ordinarily appear as a dim, putrid green (if your
	lighting is fluorescent).  If you can't darken the room completely
	it will be necessary for you to construct some sort of shade
	around the screen.  Also you'll want to remove fingerprints and
	dust, other crud, etc., from the screen.

2)	Use shutter speeds substantantially longer than the display's
	refresh rate.  I suggest 1/8 second or longer.  I've usually
	used 1/2 second or more.  Obviously you'll have to set your
	exposure manually.


3)	Most electronic metering systems will not properly meter a
	flickering source (like a CRT).  Older "electromechanical" meters
	will.  (Luna-Pro, cheap handheld meters, most needle-type meters
	in general.)  You can't use your camera's meter to
	read the exposure, unless it's of the electromechanical type.

4)	When you meter the screen, turn off the lights and place the meter
	directly on the display, pointing it at a NEUTRAL, relatively dim
	area.  If you're photographing a display of lines, you'll have to
	meter something else to get your exposure.  Meters are calibrated for
	a reference subject of 18% reflectance.  Ideally, you'd want to
	meter something that was 18% as luminous as your display's "white,"
	but there's usually no practical way to do this.  So you'll have
	to guess, and...

5)	BRACKET YOUR EXPOSURES.  A minimum of three exposures per display
	is advisable.  If your exposure turns out to be 1/4" at f/8, you
	should take 1 picture at 1/4" as planned, and then one at, say,
	1/6" and one at 1/3".  If you're not too sure about what you're
	doing I suggest you fire off a test roll or two.  Write down
	EVERYTHING as you conduct your test.  Bracket by half- or third-
	stops in both directions from your estimated exposure, 1 or 2 stops
	each way.  Record the settings of brightness and contrast controls
	on the display.  Be sure when you look at the results of your
	test that you view the slides properly, either in a good viewer or
	as they will be projected.  Most slides that are a half-stop
	under- or over-exposed look OK when just held up to the ceiling
	lights or whatever.

6)	If your slides have a pronounced color bias you'll need to try
	filtration.  Use CC ("color correction") filters, and experiment until
	you succeed.  This is a complicated procedure for the amateur
	photographer, but basically you'll need gelatin filters and
	a gelatin filter holder, both of which can be ordered from a good
	photo supply store.

7)	A mild telephoto lens (about "portrait length"-- 85-110 mm) is best
	unless you're photographing a particularly large screen.  Then
	you'll want an even longer lens.  You need to be far enough back
	from the display to eliminate perspective effects and to make sure
	the entire screen will be held in focus.  In particular you need
	to be far enough back from the screen to eliminate "bowing" of
	the display due to the CRT's curvature.

8)	A GOOD TRIPOD is essential.  A remote shutter release is almost
	as essential, unless you have either a self-timer or have a very
	light touch on your shutter button.

Films:  Different films react different ways to different screen phosphors.
	You might have had great luck with Ektachrome 100 on your
	VAXstation but that doesn't mean it'll work as well photographing
	your TV.  I suggest you try Ektachrome 100 or Kodachrome 64 at
	first.  If you have problems with the color balance you can always
	try a couple of other slide films before proceeding to the (ugh)
	filters.

If your results aren't good at first, keep trying.  Good slides of
computer graphics are a little tricky to make, but not impossible.

	-joseph

(I thought I'd post this instead of replying directly, since I think it's
probably of interest to a few other folks.  Sorry it it wasn't.)

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