Scaling Up a Pinhole Camera

Since the angular radius of the Sun is rather small to get a useful image of it one would need a large pinhole camera. One can solve the illuminance formula for the "pinhole" opening which would be needed to keep the same value for the illuminance.


Remember that the image radius is r_d = d·θ_S which makes d = 215·r_d. This suggests a long tubelike pinhole camera for viewing the Sun.