Sunday, August 23, 2009

Darkroom Tip-O-The-Day, Part 2

In a previous entry I had mentioned falling plate cameras, a way of overcoming the one-shot limitation to pinhole box cameras. I reinvented this idea, originally conceived in the formative years of photography in the 19th century (as King Solomon lamented, there is nothing new under the sun).

The problem with the box camera is that, although it represents a simple way of exposing large format sheet film or paper, minus the cost of a multitude of sheet film holders, it's limitation to one shot at a time renders it impractical for extended photo-safaris into scenic areas that would benefit from the acreage of large format sheet film. In an attempt to overcome this limitation, I conceived of a stack of film holders - mere matte boards, cut to size, stacked horizontally in the rear of a camera, to the front sides of each were affixed a sheet of film or paper, and a mechanism incorporated into the box permitting the front-most holder to be dropped, face down, into the bottom of the box after its exposure.

8"x8" FORMAT
The first camera I built that utilized this principle was a box constructed from 1/4" oak plywood, using a film format of 8"x8", and holding 8 matte board film holders. The front view of this camera can be seen in the title photo of this entry. The shutter, a guillotine-type of sliding shutter, can be seen in the open position.

This next image shows the rear of the camera, with the lid removed, and the stack of matte board film holders visible. There are two sets of notches cut into the matte boards, on each side. In front of the stack of holders are two sets of sliding brass pins, operated by sliding knobs on the outside of the camera, which cause the pins to slide up and down. The notches in the matte boards are cut off-center, and alternate between each board up and down.

This image shows the rear of the camera, minus the film holders, where the pins can be clearly seen.

Here are the stack of film holders arrayed out for display. There are two strips of black paper, top and bottom, behind which the 8"x10" paper is retained, providing an 8"x8" square format image area. Again, the notches in the sides of the boards alternate off-center up and down; the operation knobs are alternatively slid up and down to drop each film holder, after exposure, into the bottom of the box.

Here are the details of the rear operation knobs, the cylindrical dowel, which move up and down, operating an internal plate that moves up and down in a light trap, to which are connected the two metal pins. Also seen is the machine screw used to secure the rear lid in place. The lid has a 1/4" ridge as a light trap that mates to a 1/4" slot in the rear of the camera. There are also several springs glued to the inside of the lid which help keep the stack of matte boards pushed forward against the retaining pins. On the bottom of the camera the matte boards sit on an elevated platform, raised in height above the bottom floor of the camera enough to permit the whole stack to fall properly.

This image was taken using this camera at Casa Rinconada in the Chaco Canyon National Monument in northwestern New Mexico, using a paper negative.

The next box camera I built on the falling plate principle was smaller in size, again square format, but using 4"x4" negatives. These were cut from 8"x10" sheets of paper in the darkroom.

This first image shows the front view, with the shutter open. The frame of the camera is soldered together from sheets of galvanized steel, and covered in beige craft foam. It also uses a guillotine shutter with a brass operating tube. Sighting dots can be seen on the top and sides.

This next view shows the rear of the camera, lid removed, without film holders. The main features are the double-wall light trap, made of galvanized sheet steel, and the square brass tube mechanism on top with the protruding pin. This brass tube is actually a nest of three different sizes of square cross-section brass tubing. The outer tube is in the middle, to which is soldered the protruding square brass pin; the middle tube extends across the width of the camera's interior and is soldered to both left and right side walls; the inner tube is removable, connected to the brass knurled knob protruding from the left side. This knob and tube are used to alternatively move the protruding brass pin back and forth, left and right. The series of nested tubes acts as a light trap. On the bottom of the camera's interior is the raise shelf upon which the film holders rest, with a raised lip (about 1/4" tall) preventing the bottoms of the holders from falling off the shelf due to movement.

This next view shows the rear of the camera with the film holders in place. The brass retaining pin is currently keeping the front-most plate from falling. This camera can hold eight film holders. The paper negatives are merely taped to the front of each holder using a loop of painter's masking tape. The exact distance from pinhole to film plate is not critical, due to pinhole's almost infinite depth of focus. Were this camera to use a glass lens, the exact positions of the film plates and negatives would be much more critical.

This next image shows the inner brass tube/knurled knob has been removed from the left side and inserted into the right side, which slides the brass pin to the left. You can now see the brass pin aligns with the notch in the top of the front-most film holder, permitting it to fall face down into the bottom of the camera. The camera has to be gently tilted forward for this to happen; I also try to listen carefully for the subtle sound of the plate falling.

Here is an abstract composition captured using this camera onto Freestyle's APHS litho film.

5"x8" FORMAT

Pleased with the smaller 4"X4" format's portability, I wanted an intermediate sized camera. I chose the 5"x8" format, although this camera can also do 5"x7" and also 6"x9.5". This camera was actually originally conceived to use sheets cut from a roll of aerographic surveillance film, 9.5" wide, but the thin-based film proved to be too curled for this type of film holder to successfully manage. I can cut two 5"x8" sheets from a single 8"x10" sheet of paper, or a single 6"x9.5" sheet.

This front view shows the guillotine shutter in its open position. Viewing dots are on the top and sides to aid in composition. The large black knob on top rear is the film changing knob. The hinged plywood base was added after construction in order to add additional weight to the camera. Normally lack of weight is not a problem with large format box cameras, but in the case of this camera it was built very efficiently, from a space frame of 1/4" hardwood square dowels and covered in sheet aluminum flashing using JB Weld epoxy cement. The hinged base also permits use of my homemade large format wooden tripod, which lacks an articulating head.

This next image shows one of the film holders with a paper negative already mounted. I had forgotten about this negative being in the camera, and discovered it only when I setup the camera to be photographed for this article. It's now toast. The paper negative is secured to the holder by several loops of painter's masking tape. The holder itself is made from sheet aluminum flashing, spray painted first with metal primer, then flat black paint. The off-center notch is seen in the top of the holder.

Here we see the film holder mounted in the camera, with the retaining pin capturing the front-most holder from falling. The operating knob works a sliding wooden plate built into the 1/4" thickness of the camera's frame, whose threaded bolt protrudes out to act as the retaining pin.

This image shows the operating knob has been slid to the left, permitting the retaining pin to now align with the notch in the front-most film holder, permitting it to fall to the camera's bottom when tilted forward. This camera operates very smoothly and efficiently, but the film holders fall so silently I often wonder if they work properly when out in the field. Also, the camera's interior is covered in adhesive craft felt, a great light absorber.

Here is an image captured onto a paper negative using this camera, at the Sandstone Overlook in the El Malpais National Monument in western New Mexico.

Well, there you have it. Now you all can go out and make your very own falling plate box cameras. I will be expecting some reports soon. ;)



Blogger Olivander said...

As you note, being a pinhole camera, the focal length is not critical. But if you did want to ensure that each plate maintained the same film plane, you could borrow the solution from early magazine box cameras and install a tensioned bar spring on the rear door. The bar presses against the back of the last plate, pushing the entire set forward to the fixed film plane as each plate is dropped. You can barely see it in this cutaway of a Conley Model III:

I've often wondered how the glass plates kept from shattering as they smashed one atop another to the bottom of the camera.

10:21 PM  
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