Path: utzoo!utgpu!water!watmath!onfcanim!dave
From: dave@onfcanim.UUCP (Dave Martindale)
Newsgroups: comp.graphics
Subject: Re: High-quality slides from graphics terminals
Message-ID: <15519@onfcanim.UUCP>
Date: 23 Dec 87 05:33:21 GMT
References: <3286@soma.bcm.tmc.edu>
Reply-To: dave@onfcanim.UUCP (Dave Martindale)
Organization: National Film Board / Office national du film, Montreal
Lines: 44

In article <3286@soma.bcm.tmc.edu> rick@soma.bcm.tmc.edu (Rick Gray) writes:
>We are currently investigating ways to obtain high-quality color slides
>from our Masscomp displays. [ ..... ]
>The options we are working on now are:
>
>1) Directly photographing the screen of an Aurora (1152x910) with a 35 mm 
>   camera, using either Ektachrome or Polaroid Polachrome film.  This 
>   provides pretty good slides, but it's tricky to get even brightness
>   across the slide, and the image has to be reduced to ~75% to reduce 
>   visible curvature.

If the brightness change across the image is due to the monitor (measure with
a spotmeter, or use a reflected light meter up close), look for a better
monitor if you can.  However, light falloff at the edges is also produced
when you use a camera lens wide open.  Closing the aperture a couple of stops
will help considerably.

If the image on the screen itself has curved sides, try to adjust the
monitor's pincushion correction to fix it.  If the curvature appears only
on your photographs, it's because the CRT face itself is curved and the
camera lens is designed to image a flat plane onto the film with
minimal distortion.  To reduce this, use as long a focal length of lens
on the camera as you can manage in the space available.  (This may help
edge darkening problems too).

>1) Is there any way, preferably through software, to slow down the
>   horizontal scan rate on any of the graphics processors so we can use the
>   Polaroid Freeze-frame with our Masscomps?  If that's not possible, is 
>   there any way we can build a circuit to make the output compatible
>   with the Polaroid unit?  [We can build practically any circuit, but 
>   buying a $10K+ film recorder is not an option for us.]

I don't know about the Masscomp hardware, but you might not want to do
it anyway, since you will then be limited to about 640x480 at best
in resolution.  If you can live with the reduced resolution, and the
Masscomp frame buffer can't put out NTSC timings, there are scan conversion
boxes around to convert the video signal to NTSC.  However, they cost
more than $10K, and suffer from the same resolution limitation.

For more info on generating standard video, see "The Usable Intersection
of PC Graphics and NTSC Video Recording", Tom DeFanti and Don Sandin,
IEEE Computer Graphics and Applications, Vol 7 #10 (Oct 1987).

	Dave Martindale