I am an artist with some knowledge of physics and I am trying to build a pinhole camera to expose photographic film using sunlight that passes through a filter, pinholes and Young's slits. I would like to photograph an interference pattern using the sun as the subject. My prototype camera isn't working and I wonder if anyone could help? I positioned a digital camera at the film plane and took long exposures but the images I got are without fringes - eg a blurry garden shed without any kind of ghosting or evidence of fringes. The final quality of the image isn't important - blurry or not - as long as there are fringes of some description. I wonder if I am capturing only one of the fringes and missing others appearing either side? My next thought was that perhaps the light is not coherent enough, and that this was a major issue. The current prototype camera consists of: | red filter | pinhole | pinhole | Young's slits | film plane | I understand that sunlight is not the same as laser light, but I'm using a red photographic filter to try to make the light monochromatic. I am hoping that light passing through two pinholes will increase the degree to which it is collimated (but would sunlight be collimated enough at this distance for this to work without the pinholes? Would one pinhole positioned in front of the Young's slits be sufficient?) I guess there is an issue with coherence - is it possible to make the sunlight coherent enough to allow this to work? Could I filter it somehow? Would building a Mitchelson interferometer arrangement within the camera be of any use to me? The pinholes are made using a needle to drill aluminium from a drinks can. The double slits are made using finely cut and taped pieces of an aluminium drinks can - I can achieve fringes using a laser pointer shone directly at the slits (out of the camera). The initial pinholes are about 50mm apart. The slits are about 250mm behind the last pinhole, and the film plane is about 250mm behind the slits. I'm about to build a second better prototype camera with 140mm separation beween the slits and the film plane, but I'm not sure how far I should separate the initial pinholes, whether I should remove one, or how far the final pinhole need to be from the slits. Any help would be very greatly appreciated, many thanks in advance.