This camera was orginally made to use a 90mm angulon lens with a fixed focusing. With very little modifications the lens plate was fitted with a pinhole, that is removable. When I want to focus this camera I insert another pinhole that represents f/64. Then with a focus cloth there is enough light to align the camera for the desired image.
This pinhole camera is made from a 4L latex paint can. I cut away some of the front part of the can so that the focal length would be 120mm. On the inside of the can about 50mm from the bottom I soldered a short strip of metal to keep the paper negative (100 x 254mm) in place. To hold the ends of the paper negative are soldered thin strips of metal.
The focal length V=120mm(4.72"). dia = sqrt (.00007 * 4.72) = .46mm(.018"). f/ = 120/.46 = 260. The exposure is the same as the 4x10 above.
These pinhole cameras that use paper negatives are easy to use but limited to one picture at at time. With that in mind I thought a 35mm pinhole would be an improvement. This camera is made as all the others are from 6mm plywood. The dimensions are 160mm long x 50mm deep and 60mm high. The negative image is 25 x 75mm and make 18 per 36 exposure roll. It is a little difficult to load, but in general works very well.
The focal length V=35mm(1.37"), d=sq rt (.00007*1.37)=.0098", f/=1.37/.0098=140. A basic sunny day exposure is 2 seconds with 125 asa film.
An sample from this camera
This curved film plane camera produces a large picture 203(8") x 508(20"). If a level is used for positioning the camera, the amount of distortion is quite low. A fence for instance that is about in the center of the horizontal space will be as straight as if drawn by a ruler. As a horizontal line becomes farther from the center is starts to bend. The shorter the focal length of the camera also affect this problem.
The latest experiment with a pinhole is a curved film plane 120 camera. I was interested in a large ratio image. The camera produces 4 negatives on 120 film that cover 120' and measure 60x170mm. There is an opening in the back of the camera so that the frame number is visable, I have not yet placed a red filter like the older folding cameras had years ago. The design of the curved film plane is the same as on the 35mm camera.
The camera is 240mm long x 100mm deep x 100mm wide. The film slides very easily over the curved back, I was thinking that if the tension was too great on the film that it might collapse through the film guides, but with the paper backing it work well.
To load the film there are two spring loaded knobs on the top of the camera, the film transfers from the right to the left. Lifting the knob by 8mm allows enough room to insert the film spool on the pins. The leader is pulled over the film plane and under a roller onto the take up spool (this spool is about 10mm(3/8") from the roller so it takes a little patience to get it going). It doesn't appear to require a tension plate against the film, there's enough tension on the spools to keep the film flat against the plane. The negative look reasonable and will take only slight exposure modification to get it right.
The shutters that I have made so far have all been 6mm plywood. I have found that I'm tripping over my fingers trying to close it fast enough. With this camera I have made the shutter from the same tin as the film plane. I have added a a small piece of brass that a cable release screws into. At the same position on the shutter is a small right angle bracket that the cable release pushed against. since the shutter is spring loaded as soon as the cable release is let go the shutter closes very quickly. Just under the shutter on the left is a small lock to prevent accidently exposures.
The last few pinhole cameras have been made with a focal length generally about 75mm(2.95") with a film plane of about 170mm(6.7"). This design makes the camera too deep to comfortable load the film. As illustrated above, my latest pinhole is in 2 pieces. The outside has been finished in walnut and mahogany stains, with several coats of water based urethane. The inside has not yet been blackened, so that the details are more easily seen. The basic film carrier is made from thin gauge tin, soldered to its final shape. The film rollers are made from a 3mm(1/8") brazing rod, with the ends turned to a smaller diameter and are placed in 2 holes that allow them to turn freely.
The interior parts have now been blackened with flat black (2 coats). The right hand side may appear to be lighter in color, it has been rubbed with a wax mixture so that it will slide into position easier.
The front of the pinhole with shutter and cable release(as described previously). I have not decided how to hold the 2 piece together yet, there is a strong friction fit, which may be sufficient, Further test will be required.
The back of the camera has a 12mm(1/2") hole with a 25mm(1") rotating cover. The numbers are easily seen through this hole(# 2,5,8,11) are used for the 4 exposures, this allows about 20mm(3/4") between each image on the roll of film.
I have been asked over the last little while about the size of these pinhole cameras. This group photo will show relative size. The longest camera(lower left) #3 is 250mm(10").
