THE 8 x 10 Enlarger

For negatives larger than 4x51 have had built a horizontal enlarger from an old 11 x 14 studio portrait camera. It is often far more economical to build an 8 x 10 enlarger than to purchase one, since the basic structure can be an 8 x 10 or 11 x 14 camera (without impairing its use as a camera). The camera and lamp assembly can rest hori-

Figure 2-9. The 8x10 enlarger. My enlarger was adapted from an old 11 x 14-ineh studio portrait camera in 1936, and has been improved and added to over the years. Simpler enlarging cameras can, of course, be adapted from flat-bed view cameras, or a good carpenter-mechanic can build one to specifications. Professional enlargers in 8 x 10 or larger formats are available, new or used, and are expensive.

My enlarger rests independently on tracks mounted in the concrete floor. The camera itself has limited bellows extension, so the lensboard shown is adapted for lenses of long focal length. A Color-Tran control box on the left allows the bank of tungsten lights to be set at varying intensities; each of the 36 lamps is on a separate circuit, cross-wired so they relate to the pro-iccted image (the upper-right switch controls the lower-left lamp, etc.|. Cold-light tubes replace the tungsten light when required, controlled by an off-on switch and the Horowitz stabilizer (which maintains a remarkably constant intensity of light under voltage changcs and tube heating|.

While the camera is sturdy, I found it advisable to add an additional support; the adjustable rod on the right serves to minimize vibration. The wall behind the enlarger is flat black. The light-gray parts of the enlarger do not reflect perceptible amounts of light, but it has been my intention for many years to paint them black as a matter of principle!

Colortran Enlarger

zontally on a secure shelf or table, facing a vertical easel (see Figure 2-3). The camera and lamp housing must, of course, be firmly supported; the supporting frame for my 8x10 enlarger rests on triangular tracks in the cement floor that also support the vertical easel. An alternative is to suspend the camera assembly and easel from strong overhead rails; this arrangement is somewhat simpler to operate and saves floor space for storage and other uses. Whether a floor- or ceiling-mounted enlarger track is best may depend on the nature of the building: if there is a wooden floor above with people walking on it, vibrations are likely to be troublesome with any ceiling-mounted system.

The lighting unit can be assembled by a good electrician, using a mercury-vapor grid, a bank of closely spaced fluorescent tubes, or even a simple bank of tungsten bulbs. Especially with tungsten bulbs, a forced-air ventilation system is needed, and the fan must be isolated from the enlarger to avoid vibration. I have the fan mounted on a separate small "truck" on rubber wheels, with a flexible air duct connected to the lamp housing. This unit follows the enlarger on its tracks.

For many years I used a bank of thirty-six 50-watt tungsten reflector lamps in my horizontal enlarger, with a diffusing screen of

8x10 Horizontal Enlarger

Figure 2-10. Light sources for the 8x10 enlarger. The 36 tungsten reflector-floodlights are located in a hinged back with individual switches for each bulb at the rear (visible in Figure 2-3]. The lamp housing is attached to a fan by a flexible hose at bottom, and the two prominent air outlets can be seen at top. Note that the outer rows of lights are about one inch closer to the negative plane; this slightly increases the light intensity near the edges of the negative and minimizes possible fall-off of illumination.

The two-grid cold-light system slips in place in front of the tungsten bulbs, with the latter, of course, switched off. It produces strong bluish light, which considerably reduces the printing exposure times.

opal glass. Each of the bulbs was on a separate switch, so I was able to deliberately hold back exposure of broad areas of the negative to seepage 102 give them approximate "dodging." I have since replaced this unit with a powerful cold-light system that greatly reduces exposure See page 48 times, thereby avoiding the reciprocity effect. <

The easel for horizontal projection can be a large panel that moves on the same tracks as the enlarger assembly. Adjustment of enlargement size is accomplished by moving either the easel or the enlarger. The dimensions of the easel should be larger than the greatest dimensions of enlargements to be made, to allow placement of the paper in various positions in the full image field. (The maximum projection size possible in the available space for a particular negative size and lens focal length can be calculated using the lens formulas in the Appendix to Book 1.) To ensure that the easel is aligned, it must be positioned so that the lens axis of the enlarger is centered on it and perpendicular to it.

I now use a vertical easel measuring 44 x 80 inches, with adjustable rods at the top to hold 20- or 40-inch-wide rolls of paper. The easel is precisely vertical and moves along the tracks powered by a small electric motor. It is positioned between my 8x10 enlarger and the smaller Beseler unit, and thus it can be used with either enlarger. The easel was constructed of particle board and covered with thin rolled-steel sheets attached to both sides with epoxy adhesive. The metal was painted about 20-percent gray. Paper is held in place with magnetic strips. I have a magnetic corner piece that ensures accurate positioning of two edges of the paper, with '/a-inch margins; the free edges are then held with additional magnets.

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Responses

  • Catriona Watt
    How to align easel with horizontal enlarger?
    6 years ago

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