My prototype camera makes two 6x17cm images on a full sheet of 5x7" film. Anyone with good workshop skills can build a similar large format camera or modify an existing one. The index lines mark the zero point for lens rise and fall, with up/down film movement achieved by the slotted rear standards.

From The Ground Up
I built the camera shown here from component parts found around the shop, but the same concept can be applied to an existing camera. Working from the ground up gave me full design control, but it took quite a bit of time and labor. Although the investment in both drops by modifying a camera, think the project through carefully before starting. Considerable patience and workshop skill are required, making this a Level 4 project. Because of the many variables in an undertaking of this sort, I feel a procedural overview will be more useful than a step by step guide.

Find the center point of each image as described in the text and determine the amount of travel needed. A wooden separator strip is fastened to the outside of the ground glass with double-sided tape to speed composition. Although the entire image produced by the lens is visible on the ground glass, the masked film in the holder records only what is seen in the top or bottom half. With two masking slides, three images can be made on a single sheet of film.

Adding lock screws, made by setting 1/4x20 threaded studs into the camera back, and slotted vertical standards, machined from aluminum flat stock, provides this travel. Mechan-ical details will be dictated by the camera being modified, but screw placement and slot length must produce at least the amount of movement shown in the Center-to-Center diagram. It is also important that the slots be straight and parallel so that the film plane remains at right angles to the optical axis.

Bellows Flex
Appraise your camera carefully before starting. The bellows must flex enough for the significant additional rear travel, yet extend and compress adequately for the lens(es) you plan to use. The now limited bellows may require a recessed lensboard to focus short focal length lenses, or an extension cone to accommodate long ones. (See my DIY article in the April 2000 issue for an economical way to make these.) While not an inexpensive item, a bag bellows solves a host of problems. The pleated 8x10 bellows cut to fit the 5x7 camera back shown here has a range of 135-300mm with a flat lensboard.

Perspective control movements not present on the existing camera can often be incorporated into the new rear standards. My prototype has only rear swing, but a pivot arrangement would add base tilt and a slot in the bottom bar would provide shift. The level of sophistication is up to you, but I highly recommend making a full-size drawing of the camera and all proposed parts first to check for mechanical interference. Keep in mind that more bellows flexibility will be needed with added movements.

Using the panoramic mask requires a few more steps than a conventional dark slide, but practice makes perfect. Stick bits of tape to both sides of the holder and pull them off after exposing each half-side. Identify the masking slide clearly with red tape to avoid exposure accidents.

Film Holder Selection
As film holders of the same format vary in size, use a set of identical ones from the same manufacturer. Determine the size and exact center points of the masking slide by inserting a sheet of paper into a holder and tracing around the inside with a sharp pencil. Remove the paper and carefully draw a 5mm margin down the center. Measure from the traced line to the beginning of the margin and mark the center of each half-sheet. The center-to-center distance, or total travel of the rear standard, is the distance between these two points. Cut the masking slide to just cover the center margin.

Mark the slide and drill a small hole where the two lines intersect to eliminate a crack-prone square corner. Score the fiber material deeply with a sharp knife guided by a straightedge, then gently flex it back and forth while watching the opposite side for a stress line. When this line becomes visible, flatten the slide, score along the new line and continue to flex until separation. Smooth the edge with fine sandpaper. Spare slides for 4x5, 5x7, and 8x10 holders are available from pro equipment dealers.

Although it may seem that normal front rise and fall could be used to accomplish the center-to-center shift, remember that even slight lens displacement significantly alters the perspective of the scene. With the sliding action located at the rear of the camera, the top-to-bottom change moves only fresh film into position and makes both exposures from the same point of view. Movement can be made in other ways, such as by mounting the rear of the camera far off-center and turning a four-way or rotating back 180 between exposures, so think about your modification.