As mentioned in the thread about the 5 quid large format lens which was originally on a knackered Adox 6x9 folder, my plan was to make a pinhole camera from the body. I finally got round to doing it a few days ago, and here's the result...
You can't see the bellows here, but this was retained and used as the mounting surface for the plate with the pinhole - no point in taking it off and then trying to make the front light tight when it already is. To the left and right, under the black gaffer tape, there's a bit of 3mm ply (the 0.3 sticker is near the top of one bit of ply), and the inner edge of each piece is lodged into the first fold of the bellows such that the front is held out. The gaffer tape then holds the bits of ply in place. The pinhole plate was then placed over the opening and held down with more gaffer tape. The bit of insulating tape is the no-lens cap and is folded back on itself at one end to make it easier to get a hold of when removing it. It's not the shutter due to the risk of the camera moving when it's pulled off - what I do is get a finger over the pinhole as I pull the tape off and then remove and replace the finger as the actual shutter.
Here's a close-up of the pinhole plate...
In the centre, you can just make out the pinhole. It's 0.3mm in diameter and the plate is 0.05mm stainless steel shim. The hole was made using a very small carbide drill in a small milling machine (not advisable to use a carbide drill this small in a hand-held drill - they are extremely fragile and any sideways force or tilt can snap the drill).
The size was somewhat arbitrary. This pinhole was originally on a 5x4 lens board (along with another at 0.4mm, hence the sticker so that I could tell which was which). It just so happened that it worked out about right in terms of diffraction - the distance from the pinhole to the film is just about 35mm, and the calculated ideal for this was 0.28mm. Close enough. The effective aperture is f/117, so I used f/128 as the nearest proper stop for the purpose of metering.
Before doing the tape stuff, I had to do some fixing to the internals...
The little slidey things that hold the spools in were a bit grotty, and a squirt with silicone oil on each sorted that out (followed by a wipe with a rag to get the overspray off). The catch for the back was also yucky - dismantled and some lighter fluid followed by some Castrol Magnatec (both applied with small paint brushes), and a resetting of the spring, took care of that. The two tabs that put tension on the spools had a fair bit of surface rust, so they were sanded with some fine emery. The blue cross on the back of the pinhole plate was to help with getting it centred when taping it on (easier to see).
One other thing that I needed to do was to make the bottom part that holds the supply spool...
When I got the camera a few years ago, this was missing, which meant there was a big hole underneath where the tripod socket is, as well as the lack of retention of the bottom of the spool. Since I had bought a second Adox folder, I had an existing one to use as a guide, and I made this one from aluminium on a lathe. The original plan was to make three little holes around the side and use screws to hold it in place (that's how the original was fitted). As it turned out, some blobs of medium viscosity superglue were the quicker and easier solution. The bit of metal with the tripod socket protrudes into the cavity, and there's a recess on the underside of the aluminium part, so there's a natural light trap there (transparency of the glue isn't an issue).
One other thing that can't be seen here is copper tape that was used to blank out some holes in the body on either side of the bellows. These resulted from drilling out rivets that held on some of the folding arm gubbins when it had a lens. Some were in the top and bottom plates outside the bellows, but there was one in each of the side faces in beside the bellows, and these passed light into the film chamber. Self-adhesive copper tape was the easiest fix (sticks well, and is utterly light tight).
I went out and shot a test roll today. Overcast and a bit dull. Exposures were all about 1 second or so (or as near as I could count 'thousand-one' and remember to get my finger back over the hole at the end). The negs are drying, and look okay. If anything, maybe some more exposure would have been better, but there should be enough to get decent scans. There is some quite noticeable fall-off towards the ends/corners, which is expected - a 35mm focal length on this size is about 14mm on a 35mm camera, meaning that the effective area of the pinhole encountered by rays coming in from oblique angles is reduced quite a lot (about 1/3rd or less at the corners once the thickness of the pinhole plate is accounted for).
I'm happy to report that the tension stuff works well - the take-up spool was wound nice and tight when I unloaded it at home (in rather subdued light). No qualms about shooting two rolls outside and reloading in the field.
Pictures to follow.
You can't see the bellows here, but this was retained and used as the mounting surface for the plate with the pinhole - no point in taking it off and then trying to make the front light tight when it already is. To the left and right, under the black gaffer tape, there's a bit of 3mm ply (the 0.3 sticker is near the top of one bit of ply), and the inner edge of each piece is lodged into the first fold of the bellows such that the front is held out. The gaffer tape then holds the bits of ply in place. The pinhole plate was then placed over the opening and held down with more gaffer tape. The bit of insulating tape is the no-lens cap and is folded back on itself at one end to make it easier to get a hold of when removing it. It's not the shutter due to the risk of the camera moving when it's pulled off - what I do is get a finger over the pinhole as I pull the tape off and then remove and replace the finger as the actual shutter.
Here's a close-up of the pinhole plate...
In the centre, you can just make out the pinhole. It's 0.3mm in diameter and the plate is 0.05mm stainless steel shim. The hole was made using a very small carbide drill in a small milling machine (not advisable to use a carbide drill this small in a hand-held drill - they are extremely fragile and any sideways force or tilt can snap the drill).
The size was somewhat arbitrary. This pinhole was originally on a 5x4 lens board (along with another at 0.4mm, hence the sticker so that I could tell which was which). It just so happened that it worked out about right in terms of diffraction - the distance from the pinhole to the film is just about 35mm, and the calculated ideal for this was 0.28mm. Close enough. The effective aperture is f/117, so I used f/128 as the nearest proper stop for the purpose of metering.
Before doing the tape stuff, I had to do some fixing to the internals...
The little slidey things that hold the spools in were a bit grotty, and a squirt with silicone oil on each sorted that out (followed by a wipe with a rag to get the overspray off). The catch for the back was also yucky - dismantled and some lighter fluid followed by some Castrol Magnatec (both applied with small paint brushes), and a resetting of the spring, took care of that. The two tabs that put tension on the spools had a fair bit of surface rust, so they were sanded with some fine emery. The blue cross on the back of the pinhole plate was to help with getting it centred when taping it on (easier to see).
One other thing that I needed to do was to make the bottom part that holds the supply spool...
When I got the camera a few years ago, this was missing, which meant there was a big hole underneath where the tripod socket is, as well as the lack of retention of the bottom of the spool. Since I had bought a second Adox folder, I had an existing one to use as a guide, and I made this one from aluminium on a lathe. The original plan was to make three little holes around the side and use screws to hold it in place (that's how the original was fitted). As it turned out, some blobs of medium viscosity superglue were the quicker and easier solution. The bit of metal with the tripod socket protrudes into the cavity, and there's a recess on the underside of the aluminium part, so there's a natural light trap there (transparency of the glue isn't an issue).
One other thing that can't be seen here is copper tape that was used to blank out some holes in the body on either side of the bellows. These resulted from drilling out rivets that held on some of the folding arm gubbins when it had a lens. Some were in the top and bottom plates outside the bellows, but there was one in each of the side faces in beside the bellows, and these passed light into the film chamber. Self-adhesive copper tape was the easiest fix (sticks well, and is utterly light tight).
I went out and shot a test roll today. Overcast and a bit dull. Exposures were all about 1 second or so (or as near as I could count 'thousand-one' and remember to get my finger back over the hole at the end). The negs are drying, and look okay. If anything, maybe some more exposure would have been better, but there should be enough to get decent scans. There is some quite noticeable fall-off towards the ends/corners, which is expected - a 35mm focal length on this size is about 14mm on a 35mm camera, meaning that the effective area of the pinhole encountered by rays coming in from oblique angles is reduced quite a lot (about 1/3rd or less at the corners once the thickness of the pinhole plate is accounted for).
I'm happy to report that the tension stuff works well - the take-up spool was wound nice and tight when I unloaded it at home (in rather subdued light). No qualms about shooting two rolls outside and reloading in the field.
Pictures to follow.
