Hi folks. I am intrigued with the possibility of building a pinhole camera for taking photos of the sun. Has anyone done this, and if so can you comment? Here are a few parameters I am thinking about. First, I think the "focal length" should be very long in order to provide a large image on, let us say, a medium format film, or maybe even large format film. Regarding the focal length, we are probably talking about several feet long. For optimal resolution the diameter of the pinhole should be proportional to the square root of the focal length. This means that there will be a loss of image brightness on the film plane, i.e. the brightness will be inversely proportional to the focal length. I don't think the loss of image brightness is going to be much of a negative issue because the sun is so enormously bright to begin with. Aiming of the device might be a bit of an issue. I am thinking that one should stack the pinhole camera and a pinhole viewer. Mounting the camera might be a problem too. What do you think?