Photographing the computer screen

Why photograph a computer screen?

Photographing a computer monitor screen is of interest to two entirely different types of photographers. The first is the photographer who is contemplating purchasing or who already has a computer used for home applications such as household budgets, educational software, games, and the like. Although these machines are not purchased with digital photography in mind, using a draw (or illustration) program (which frequently comes "bundled" with the machine when it is purchased), professional-looking slides containing stunning text and artwork can be produced quickly and easily. Even if they have to be purchased, draw programs with hundreds of fonts and thousands of art clips of high quality can be obtained for a remarkably low price.

If you are the second type of photographer, i.e., the sort that considers computers as another hobby, then by using a paint (or imaging) program, photographs can be manipulated in a way just not possible by any other technique. Although "screen shots" involving photographs will generally not be of competition-quality (this depends upon how highly the judge rates resolution over the other factors and, of course, on the rules governing computer images in a specific competition), in slide shows the loss of resolution in a screen shot is more than made up for by images that will make your audience sit up and notice with awe. Regardless of which type of photographer you may be, the advantages in photographing the computer screen are, in addition to its convenience, its speed and low cost. A "screen shot" costs about 30 cents; any other method is far more expensive, much slower, and definitely a lot less convenient.

Photographing the Computer Screen: The Details

Photographing a computer screen involves five basic operations: (1) monitor adjustments, (2) insuring that the image to be photographed lies within the boundaries of what the film can see, (3) selecting a lens with closeup capability and fitting it with an appropriate color-compensating filter, (4) insuring that the camera is positioned so that the plane of the computer screen is parallel to that of the film, and (5) some preliminary experimentation to determine an appropriate aperture and shutter speed.

Preliminary Monitor Adjustments: Geometry

Before anything else, the monitor must be adjusted so that the geometry of a screen image is correct. This means that any box drawn on the screen is truly rectangular, i.e., the four lines must be straight, opposing sides must be parallel, and the lines at each comer must be at 90 degrees. Inexpensive monitors will have fewer adjustments for geometry than more expensive ones so you will have to make the best adjustments possible, given the controls available. Here is where it pays to carefully read the instruction booklet that came with your monitor so you know what controls for geometry are available and what each one does.

Adjusting Monitor Brightness

All computer monitors come with an adjustment for brightness, and this is usually set to produce the most comfortable viewing under the existing ambient light of the room in which the computer is placed. The computer screen, however, will be photographed with the room in complete darkness. It is important to set this control so that, under these conditions, black is truly black and not gray. What looks black with the lights on may not look black with the lights off and, more importantly, may not photograph black. The degree of adjustment is a combination of your visual judgment and some trial and error. Make an adjustment and then examine the slides. When you are satisfied, never touch these controls again. Since I do not want to be bothered changing these settings back and forth as I move between room light and complete darkness, my computer screen is always adjusted for complete darkness. After a while you get used to it and wonder why other people's screens look so bright!

Adjusting Monitor Contrast Not Needed

Although photographing the computer screen with daylight film adds some contrast, it is not as bad as duping slides using daylight film, a practice which does add noticeable contrast. Adjustments for contrast are not needed for non-photographic images such as type and clip art. If you need some correction for photographic images, this should be done with the paint of imaging program, not the contrast adjustment that comes with the computer monitor. The contrast adjustment should be set to the monitor default, or a normal viewing level, and left in that position.

Checking Aspect Ratio

The aspect ratio (i.e., the ratio of width to height) of the image on the computer screen is not the same as that of the 35mm image since the nominal aspect ratio of the former is typically 4 to 3 while that of the 35mm format is always exactly 3 to 2. Thus you must waste" some space at the top and bottom of the screen to insure that all of the image you are photographing will be contained within the viewfinder (and hence on the film) when you photograph. In draw programs that can preset the drawing area to the aspect ratio of a slide, a check is not needed. In other programs you can draw a box of cor rect aspect ratio, keep your image within the box, and then photograph close enough so that the box does not show in the viewfinder (and a little extra so that it will not show on the film either! .

Monitor Distortion

The horizontal and vertical size controls that are present on all monitors are typically used to minimize the border area around the image. These change the actual aspect ratio and, if not set properly, can distort the image. Distortion is usually not a problem unless the image in question is a photographic one (we don't want to make a fat bear into a slim one, for example). Draw and paint programs can tell you what the assumed size of the image is, either directly or by having the program place rulers on the image. Therefore construct a box with a 3 to 2 aspect ratio according to the program's rulers or size command and then, holding a ruler close to the screen (not against the screen- this is made of plastic and easily scratched), adjust the aspect ratio with these two controls until it is 3 to 2. Then, never touch these controls again.

Lenses

Photographing the screen is semicloseup photography so you will need to use either a macro lens, extension tubes or supplementary closeup lenses on standard lenses in order to focus the image. If you don't have a macro lens, use the cheaper solution, i.e., supplementary closeup lenses. They will do the job very nicely for text and title slides. I myself find the 60mm macro lens to be ideal. With its built-in bellows, focusing is convenient and optical quality is high. A 105mm macro lens takes you too far from the computer screen to manipulate the keyboard and the camera controls without brushing against the tripod and destroying focus and other settings.

Color Compensation

The color temperature of computer monitors is typically 9000 degrees Kelvin, whereas the color film you will be using is designed for about 5500 degrees Kelvin. Therefore a color compensating filter must be used. I recommend the Kenko TV conversion filter which takes it down to about 6000 degrees Kelvin. This filter is obtainable from The Filter Connection (P.O. Box 155, South Windham, CT 06266, (203) 456-3990) and other sources.

Positioning the Camera and the Screen

Computer screens are not perfectly flat, so in order to maximize the depth of field you must make sure that the plane of the computer screen is parallel to that of the film. Furthermore, if these two planes are not parallel, rectangles become trapezoids on your film and the image is distorted. A helpful device is a box test image (in a 3 to 2 aspect ratio) containing numerous horizontal and vertical lines (use bright colors so the lines stand out on the screen; my box is bright red with white lines). This will be your permanent "Focus/Parallax Box" so save it in a file. After positioning the tripod (a three-way pan head and a two-way macro-focusing rail helps in this chore) and focusing the camera on the lines in the box, adjust the tilt of the computer screen if you have a tilting stand for the monitor, or the tripod head, or both, so that the vertical lines are vertical and the horizontal lines are horizontal. I use an old Majestic, large-format tripod that tilts every which way you can imagine, two-way spirit levels on both the monitor and the tripod base, a two-way macrofocusing rail, and a tilting monitor base; nonetheless, this still is the most time-consuming adjustment I have to make in the whole screen photographing process.

Exposure

To determine your exposure settings, construct another 3 to 2 aspect ratio box and fill it with a gray that looks to you (with the lights off) roughly like an 18 percent or medium gray tone. This will be your "Exposure Box" and also saved in a file. Let your camera meter pick a base exposure automatically, and then photograph this box varying the aperture and shutter speed manually around this base setting, and record the information. Compare the results with what you see on the screen (I usually project the slides with the projection screen as far from the computer as possible so light does not spill from the projector screen to the computer screen, and then I glance back and forth between the screens to make my comparisons). This determines your standard speed/aperture settings and will not be changed unless you change monitors, readjust brightness or contrast on the monitor, or change film.

Setting my camera manually to this standard setting, I then bring up the Exposure box and alter the shade of gray in the box so that it produces the correct exposure reading at this standard setting. The box is saved. Then, whenever I photograph the screen I first bring up the Focus/Parallax box to: (1) adjust for focus, (2) insure that all of the image will be captured on the film--precisely that and no more (we don't want the sides of the monitor showing up in the image), and (3) adjust for any distortion. Then I bring up the Exposure box and manually set the camera exposure from a reading from it. (I could, of course, omit the Exposure box step and just use the standard exposure settings, but this is an added safety precaution to insure that the monitor settings have not been altered since the last shoot. Then I just bring up one image after the other and shoot!

What your own particular standard exposure settings will be will depend upon your monitor, how you adjust contrast and brightness, and other miscellaneous factors. That said, my current standard exposure, using Fuji Sensia 100, a 60mm Nikkor macro lens, the Kenko TV filter, and a 17-inch NEC XP17 computer screen, is one second at an aperture halfway between f/4 and f/5.6. Others with brighter monitors might be able to decrease the aperture and thus obtain a greater depth of field. Because of color shifts with long exposures, I would not recommend exposures of longer than one second. Within this limitation, however, use the longest exposure you can so that you can use the smallest possible aperture.

Bezel Reflections

Finally, most computer screen housings are a shiny gray or beige and the bezels (the slanting portion of the screen housing) will reflect light from the image back into it, causing flare in the image when it is photographed. Because the computer screen is larger vertically than the image, this reflection is a problem usually only on the sides, the top and bottom of the screen housing being too far away from the image to reflect light back into it. You can glue a strip of flat-black construction paper (the old, flat-black electrician's tape will also do) to the side bezels of the screen housing or, if you are not concerned about the resale value of your monitor, even paint them with a flat black paint as I do. This may be the last point made in this article but it is by no means the least important, as flare can ruin any picture, no matter what you are photographing.

Summary

As you are now probably aware, although photographing the computer screen is an easy enough process, it is not one simply of pointing your camera at the screen and pressing the shutter release. There are a number of important details that must be attended to if you are to obtain high-quality results. In either case--whether you have trouble finding the off/on switch on your children's computer after they have gone to bed, or you are a gung-ho digital imager with the latest electronic toys--attention to details pays off handsomely!

COPYRIGHT 1995 Photographic Society of America, Inc.
COPYRIGHT 2004 Gale Group