diskMAGazine (Apr 1991) : ScreenPhotos


Contributed by Robert Goldberg, M.D.

     I have shot some two dozen rolls of film now off the Amiga screen, and
I wanted to share my experience using various techniques.  My current setup
produces spectacular color slides which project very well, even onto a
large screen.  I personally use the slides to illustrate medical
lectures; anyone who needs to make presentations or promotions of any kind
should try using their Amiga to produce a set of lecture slides.  Amiga's
striking graphics are absolutely stunning when projected on a large screen
and, with a little care exercised in the production, you ought to be able
to completely dazzle your audience (especially if they have only been
exposed to the somnolent graphics produced by Amiga's competition!)  I'm
sure that Amiga slides have abundant applications in other areas as well,
such as advertising, art, and so forth.

      After a great deal of experimentation I have arrived at the following
setup for slide production.  As with anything, there are endless ways to
accomplish the same goal, and your own tastes and equipment will dictate
any necessary modifications to these recommendations.  The important thing
is to refine your setup to the point that it is simple and repeatable. -

-- CAMERA --

     Any 35mm single lens reflex will do fine.  I use a Nikon N2000.  A
sturdy tripod is key, although I suppose an extremely patient individual
could use a table with a bunch of books or something to provide a platform
for the camera.  You need to be able to manipulate the camera position very
precisely, though, as I will explain below, and a tripod is the only
efficient way to do this.
    Also, a shutter release will make your life much easier since the
exposures tend to be long, and directly pressing the camera button can
sometimes induce unacceptable vibration; if you flat refuse to get a
shutter release, a good poor man's trick is to use the camera's self timer
so that you can keep your hands off.

-- LENS --

     Your computer screen is not flat.  The curvature of the screen can
induce distortion; this is particularly noticeable when your graphics
include a large rectangular border near the edge of the screen.  This
curvature effect can be minimized (not eliminated) by using a lens of
moderately long focal length.  I have not noticed much improvement with
longer focal length than 150mm; at very long focal lengths, the camera ends
up inconveniently far from the screen and also more sensitive to vibration.
 I would recommend a lens in the 120mm to 200mm range.
     If you want to take shots of less than the full screen, you will need
a lens with some sort of close-focusing (macro) ability.  Some of the new
zoom lenses allow pretty close focusing (and the zoom capability makes it
very easy to fine-tune the desired magnification.) 
     There are three less expensive alternatives if you do not already own
a close-focusing zoom lens:

1)  (My choice:)   Use a tele-extender.  ($25-50)  I use a Vivitar 3X
tele-extender on my 50mm standard lens; this nets me a 150mm lens with
ability to focus to 2.5 feet from the screen, which is about the most
magnification that is useful (more than that and the dot pattern of the CRT
display becomes very noticeable.)  These are inexpensive and sharp; they do
reduce the effective aperature 3 stops (allow 3 times less light to get to
the film for you non-photographers) but you are on a tripod anyway, so a
slow shutter speed is no problem.

2)  Use a close-up lens. ($10-20)  These are inexpensive lenses that screw
onto the front of your lens and allow closer focusing.  A +1 lens allows
plenty of magnification, and does not reduce the aperature of the lens.
 The image quality is not as sharp, and the flatness suffers; they actually
do pretty reasonably well, though, especially if you stop down the lens
(say to f8 or f11.)  If you already have a telephoto or zoom lens, you
might at least try screwing one onto the front of the lens and give it a

3)  Extension tubes.  ($30-100)  These go in back of the lens and allow you
to focus closer to the screen.  These would be used with a telephoto or
zoom lens (as opposed to the teleconverter, which turns your regular lens
into a telephoto.)  The advantage over closeup lenses: no loss of
sharpness.  The disadvantage: cost, and reduction of effective aperature
1-2 stops.

-- FILM --

     This is the most important thing I have to teach you!  I used a great
deal of Ektachrome 400 for my slides, and this works pretty well (slight
bluish cast.)  I have also used Kodachrome 64  and this is also reasonable.
 Any slide film is reasonable.  
     But there is a new film out that is more than just reasonable; it is
FANTASTIC!  After discovering it, I will never use another roll of anything
else for screen photos.  It is 3-M CRT Recording Film, which comes in 100
ASA.  This film was designed specifically for computer screen photography,
and although I was skeptical, I am now a fanatic.  It is basically very
high contrast, high resolution, color slide film.  It also somehow allows
the dots in the CRT image to "bleed" a little so that they are not as
noticeable.  The Amiga screen comes out in a resplendent saturated rainbow
of color.  And the black background comes out inky jet black.  I don't own
stock in the company, it's just that this film really is an order of
magnitude better than any others I have tried.
     To ice the cake, it can be processed in E-6 chemistry, which simply
means that shops that advertise 2 hour slide developing can handle this
film.  I buy the film and get it developed at Village One Hour Photo on
Westwood Blvd.;  I can shoot the slides at night, drop them off on the way
to work, and pick up the slides in time for an afternoon lecture the same


     The key here is alignment.  Draw a series of concentric rectangles on
the screen, and use this to set up the camera.  You have to be perfectly
centered and perfectly perpendicular to the center of the screen to
minimize screen warp and distortion; focusing on this grid of rectangles
will allow you to best adjust the camera position.
     Darken the room as much as possible (best to shoot at night but a few
blankets over the windows will allow daylight shooting.)  Focus carefully,
and fire away!  For your first tries, you will need to bracket your
exposures to find the best one for your setup; I have settled on  f8
(actually f2.8 with 3X extender = f8) at 1 second, using the 100 ASA 3M CRT
film discussed above.  You might start with this but as I said shoot with a
series of different aperatures or shutter speeds at first until you decide
what works best.  You will find that even 1/2 f-stop makes a difference in
the color saturation, so bracket at 1/2 f-stop increments.
     It's unlikely that you would be able to use fast shutter speeds, but
just in case, remember that your shutter speed must be slower than the
screen refresh rate; stick with 1/30 second or slower to be safe.  
     Also, the brightness and contrast settings on the Amiga monitor have a
major effect on the slides; just set them in the middle (at the click stop)
and leave them there so that there is no variability from one session to
the next.


     I use Deluxe Paint in the hi-resolution mode (No flicker problem with
still photography!)   The 400-line resolution really makes a difference;
Atari owners will never present any competition here.

     I wish you luck!  The ability to photograph Amiga screens has opened a
whole new vista for me, and has become the most important function for my
computer.  I hope that you find these hints useful.