Date: Thu, 8 Oct 1998 23:05:55 -0700 (MST)
From: Kerry Mitchell
To: fractint@lists.xmission.com
Subject: Re: (fractint) Re: [fractal-art] cost of images
Here's how I make some of my photographic prints.
With a little effort and planning, you can use your camera to make quick,
colorful and relatively inexpensive prints of your fractals. Photographic
prints, when properly done, are more vibrant than inkjet prints and have
an archival lifetime much longer than inkjet prints. In this article,
I'll describe my technique for photographing the monitor and making
fractal photographs.
First, you need an image. When creating your image, you should take full
advantage of your system's capabilities. That is, you should create
images that use the highest pixel and color resolutions you can display.
For example, if you can display 1024 x 768 pixel, true color images, then
you might want to generate a 3072 x 2304 image and anti-alias it down to
1024 x 768. You can do this with an image-processing program like
Photoshop or Picture Publisher. You may also want to sharpen the image a
bit after resizing it. Make sure that your image-processing program has a
"view full image" mode, in which the complete image is shown, without any
borders or window elements visible (you don't want those in your fractal
print). If your image does not have 4:3 proportions, you may want to add
black borders around the edges. This will help you keep the image
centered in the photo view.
Next, you need a camera. It's best to use a 35mm SLR (single lens reflex,
or "through the lens" viewing) that lets you set the aperature and shutter
speed manually. You'll need a long lens (focal length of 100mm or longer)
or a zoom lens, preferably with a macro setting. This will allow you to
fill the viewfinder with the computer monitor. The long lens will also
help flatten the image, reducing the effect of the curved screen. You'll
need a tripod to steady the camera, and a cable release so you can release
the shutter without jarring the camera. Set up the camera a few feet in
front of the monitor, taking care to make sure that the camera is square
with the monitor face. Otherwise, you'll have some skewing and other
distortions in the final print. Use the zoom on the lens, or move the
camera to fill the viewfinder with the monitor image. To set the focus,
it may be helpful to toggle to a text screen, or to a screen with thin
vertical lines. (I find it better to use manual focus rather than
autofocus, as some images can confuse the camera.) It's important to use
an SLR camera, so you can set the focus with the exact same view that the
film will see. "Point and shoot", or "rangefinder", cameras, have a
slight offset between the viewfinder and the lens. At this close
distance, that offset can be critical.
To take the picture, make sure that there's no other light in the room.
Cover the windows and turn off any lamps. Any other light in the room
will tend to wash out the monitor image and may cause reflections off of
the glass. Once you have the image set in the viewfinder, you'll need to
set the aperature and the shutter speed to get an accurate exposure.
Although it may look like a static picture, you're actually photographing
a moving image. Depending on your set up, the monitor is redrawing the
picture 50 to 100 times per second. In between refreshes, the phosphors
in the monitor begin to fade. If you use a short exposure (less than 1/30
of a second), you'll probably catch the monitor between refreshes. You'll
see a dark horizontal band across the picture, where the phosphors are
fading and have not yet been refreshed. To compensate for this effect,
use a long exposure (1/2 second to 1 second). This will blur together all
the dark bands, giving a nice, bright picture.
The other setting that controls the exposure is the aperature. This is
the size of the hole through which the light comes. Normally, you use the
aperature to control the depth of field of the image, or how much of the
image is in focus. However, if your image is completely taken up by the
monitor, then just about any aperature setting will have the entire screen
in focus. Use the aperature (or f-stop) to control the light: lower
numbers (f/4 or f/5.6) to allow a lot of light in, and larger numbers
(f/11 or f/16) to reduce the light. Use your camera's meter to determine
the appropriate aperature setting.
I have found that strict adherence to the camera's metering leads to
overexposing. Therefore, be prepared to take several exposures for each
image. You should bracket your exposures, which means taking 2 or 3
pictures of the same image with different aperature settings. For
example, if the meter indicated that you should use an aperature setting
of f/8 with a shutter speed of 1 second, then you might also want to use
settings of f/11, f/16, and maybe f/22. This should ensure that you get
at least one exposure that you like. In the long run, it's better to take
multiple exposures and only use one, than it is to go through this entire
process and not have any usable pictures.
The film you use is also important. Color film (print or slide) is
classified by film speed (ASA or ISO number). The higher the speed, the
faster the image will develop on the film. The film accomplishes this by
using larger grains, the particles of emulsion that make up the picture.
When you have your images enlarged, fast film will give prints that look
"grainy". To avoid this, use slower speed film, ASA 100 or slower. This
is also necessary to allow you to use the slower shutter speeds needed to
avoid the dark bands. For prints, I use Kodak Royal Gold 100 film. Kodak
films tend to have a wider exposure lattitude, meaning that you can use
long exposure times before the fails to respond as expected. However, I
find that this film has trouble accurately reproducing cyans. Recently, I
best way to compare films is to shoot the same series of images with each
film, have then developed and printed at the same lab, and compare the
prints.
Once you've shot your roll, you have to entrust it to a photo lab for
developing and printing. Unfortunately, this step is critical to getting
good prints, and is one over which you have little control. The
developing of the film is automated and usually goes well. The printing
step is usually done by someone who may have a pretty good idea of what
people and landscapes should look like, but may have no idea how fractals
should look. This is important because the printer has a lot of power in
determining the final color of the print. Further complicating matters is
that you can never exactly match a print to what you see on the screen.
The screen image represents transmitted light, which is of a different
quality that the reflected light coming off of the print. If you decide
to take a lot of pictures of your monitor, it will be important to find a
photo lab with whom you can work and who will take direction. I use
one-hour labs, because I can give immediate feedback to the printer about
the colors. The printer will generally have control over either the red,
green, and blue channels, or the cyan, magenta, and yellow channels.
Also, they usually have a "density" control; low density makes the image
too bright and washed out, while high density makes the colors very
vibrant and dark. If possible, you should have a color guide to show the
printer how the colors should look. If you have a good color printer, you
can print one or two images and give them to the printer to match. Or,
you can create a "test pattern" of standard colors. Have the printer
correct for the test pattern, and then print all of the other images the
same way. When you get a good print of your image, use that as a color
guide when you have enlargements made.
While a bit involved, this technique provides a means of creating
photographic prints of your fractals. When you master it, you can create
small- to mid-size enlargements quickly, easily, and with minimal expense.
Have fun with it--I have.
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Kerry Mitchell
lkmitch@primenet.com www.primenet.com/~lkmitch/
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