Hello, We took several photos on a B&W film, and when we developed them, unfortunately most of the negatives were white (as if the aparture never opened (the environment was well lit)). One frame (a rectangle exactly the size of a single photo) was entirely black and there were some thinner black stripes near the beginning of the film. There were no "greys" anywere on the film. After checking the camera it appears to be alright and its aperture opens. Can anyone propose according to their experience in which stage the problem could be? The camera is Canon EOS 3000V and the film is KODAK PROFESSIONAL T-MAX 100. The development procedure was: 6 minutes in a D19 developer (mixing 10 seconds per minute) 1 minute wash in flowing water. 10 minutes in a fixer (mixing 10 seconds per minute) [I don't know it's name but it contained mostly (1 mol.) sodium thiosulfate, and a smaller amount of other chemicals. 1 minute wash in flowing water. The film itself was of course acquired as is, but the chemicals were made in our lab (by physicists, who never took a photograph on film in their life...). We're far from professionals but we did it twice before and it worked (with an other, but similar camera, though). I'll thank whoever can help.