If you haven't already solved the mystery, then it's time to narrow the possibilities. 1) Load the camera in a darkroom (or darkbag) and hand-roll forward to position the first film frame without using the winder, then close the camera. 2) Carefully bring the camera into daylight and make just one exposure; handle the camera gently (don't flex it) and touch nothing but the shutter release. 3) Process the roll (develop only) and analyze . . . If the rest of the roll remained unexposed, and your light leak is only present on the single frame exposed, put the developed negative back into the camera and the intensity and direction of the leak should point you directly to the problem. Yes, this will waste a roll of film, but to make an omlette you gotta break an egg!
It's situations like this that are a real pain. You think you have found the problem only to realise it's still there when the next text film goes through the camera. Eventually you have a eureka moment and the problem is sorted. Definitely a case of "there is light at the end of the tunnel".
If there are just a couple of holes, you might be able to cover them with gaffer's tape. Not duct tape, but gaffer's tape. It does a very good job of blocking light. It's not gooey. And it remains flexible.
I've done this before to repair holes in the bellows of a Super Ikonta III and also my Agfa Isolette III (which I need to check periodically).
A couple of ideas, although this is late to the game.
1) Get a good flashlight. Extend the lens and open the camera. Go into a totally dark room. Put the flashlight inside the bellows and see if there is any light stream through anywhere. Next, put the flashlight on the inside of the back and again look for light streaming through.
2) Make sure that the film is spooled tightly. There is a flat pressure spring on the takeup side. Carefully, bend this upward a small amount. It should maintain pressure against the spool as you wind to the next frame.
I would start with these two things. The Super Ikonta is a fairly awesome camera. One of my favorites.
I don't know how close the 531/2 is 531/16, if the latch on the 531/16 is not completely close it looks to me as there might be a possible light leak there. The 531/16 has a sliding latch on the very end of the camera (lower left) that opens when you pull it down. There are 2 notches viewed from the front of the camera latch that allow the door to open and close. So check your latch to see if it is closing all the way and is not being stopped by som obstruction. Good luck and Happy New Year!
I had not seen the post before, and had a look at the pictures, and I can confirm they are from Pinholes in the bellows, they are characteristic. Examples are given in the famous Kodak book on camera faults. For reference static marks would be different for each negative, if it is the same it is light. Only 120 roll film suffers from static if the film path folds the film around rollers in reverse, as the backing paper rubs it can make static in dry conditions. The worst offender is the Hassleblad film cassette back.
Tracing the pinholes, as you found, is not easy, it needs a very strong light on the outside really, with the bellows and camera back secured to a cardboard box, with a suitable hole in it to see into the back, then draped with a black blackout cloth, put your head under it, if needed with reading glasses on, and wait till your eyes get used to the dark, at that point any holes will show as the folds are eased. I use a 200 watt workshop flood light for such tests, but a 60 watt+ spot lamp will do fine.
As each tiny hole is traced, put a domestic pin through from the inside to mark it for repair.
My own cure is to use matt cellulose dope, (traditional synthetic enamel car paint), thinned a bit with cellulose thinners, and paint all off the interior with this. Then do the folds, papered with folded strips of black Japanese Tissue in a medium grade weight, (aero-modellers use this), and dope it, (again aero dope or the thinned cellulose paint), into place, one fold at a time, lining the whole suspect area or even the entire interior. Finally a coat of the matt black paint again. Big holes can be covered with black art grade paper then covered with the tissue and paint.
It only really works for good grade tissue paper, with the cellulose paint and dope, but it will last many years. If a fold has split, then dope on a piece of thin silk dressmakers tape, this is perfect for areas that flex a lot. You can even do the entire interior with silk tape, strip by strip.
Other paints will also work, and the paint designed to paint Rigid Vinyl plastic car bumpers is sometimes mentioned by repairers as it has "body" and will stick to anything!
However the inside of most bellows is cloth or the absorbent surface of leather, and any glue or paint will adhere well.
After the bellows is dry, (it should be dried stretched to normal position, it can have a dash of talc rubbed over the surfaces to prevent sticking. Obviously keep it out of the camera body or the lens and shutter, which should really be removed during such work. An alternative powder is Key lubricant, graphite powder.
The advantage of these methods is it keeps the vintage outside appearance intact, no need for total replacement.
Sound advice, Stephen. Being a Dutchman, what do you mean by 'Japanese Tissue'? And where can it be obtained? (As Zeiss Ikon affeccionado I have quite some folders - also ones who need this kind of repair:-( Hans
Traditionally The Japanese suppliers make a very high grade tissue, that is used by aero modellers to cover wood framed flying models. It comes in light, medium and heavy weight, in various colours. It may not come from Japan, but the type is called Japanese, as it contains a random texture pattern, no nap or grain, and it very strong for it's weight. It is a "glossy" type surface texture, as it is not like normal soft tissues. Craft shops sell, it, and in the UK, specialist aero model suppliers. I will look up net suppliers.