To see if it would be possible to capture a pinhole image of the Sun I decided to try designing a small pinhole camera. One can start out with something with a resolution of 20 lines across which would require about 300 pixels for the image of the Sun. If the pinhole is 1 mm in radius the calculations for the image resolution show that the length of the camera would have to be about 3.5 m long*. This sets the ratio d/ro = 3500. Checking to see if we have enough light we find that E/ES = 0.003.* Since the Sun is quite bright we might be able to see this level of illumination under suitable conditions. The diameter of the projected image will be about 3.3 cm.*
To evaluate illumination conditions one would have to check against what one would get by using a pinhole of known size and measuring the illumination at various distances from the pinhole. Photos of the images using a fixed camera setting would help evaluate what a camera and the eye are capable of seeing.
*Edit: I used some data from the old calculations with the 0.1 mm pinhole and noticed that I misread the log scale for the length of the camera. I probably was a little too hasty to post results. Double checking the calculations helps.